Have a gift card and curious where I should put it!
The question is too general to answer precisely. We may be able to offer guides for what people might consider, however, but they are often conditional on your preferences, bicycle type, and riding conditions.
I am a performance-oriented mainly road cyclist. Latex tubes would be it for me. They measurably decrease rolling resistance, and are arguably more puncture resistant than butyl. They do have to be inflated every day. They can be more tricky to mount and inflate. I would not recommend them to most consumers. However, this is why a better question needs to offer more detail. Latex tubes are a valid answer, but they apply to a very specific subset of cyclists. We have no indication that you belong to this subset, but we have no indication that you don't, either.
For that matter, if you frequently ride in the rain or you might like to do so, fenders could be the answer. Indeed, many performance-oriented road bikes are starting to offer fender mounts and clearance.
You specified the bicycle, but arguably comfortable cycling clothing can make a huge difference to your comfort, and it's well worth shopping around if you don't have cycling-specific clothes.
If you have a lower end bike and you're looking to go a bit faster, upgrading the tires could be an option as well. For mountain and gravel bikes, you'll want to match the tires to the terrain you expect to tackle. I am less familiar with utility bicycles, but I imagine that higher end touring style tires may also be a feasible answer.
People don't necessarily appreciate this, but your cables and housing do wear out. It isn't a scam. You can blame the second law of thermodynamics if you want, but you are relying on a mechanism in the shifter to pull a cable which in turn pulls the derailleur. Over time, dirt gets inside the housing. You may wonder why a better system hasn't developed over time. Actually, one has: electromechanical shifting systems exist, and they're invulnerable to contamination. They're also much more than a $50 upgrade. Because they're so expensive, they tend to come on top-end performance oriented bikes. And manufacturers may not necessarily support them for as long as you'd like. If a mechanical drivetrain part breaks 10 years down the road and you can't replace that part alone, you could buy a lower end mechanical groupset, or just the key parts (e.g. often older front derailleurs are compatible with newer shift levers). Doing this on electronic shift systems may not be possible, and if it is replacing parts will be much more painful anyway. This is a long way to say that you could consider replacing your cables.
Given the current state of the bike industry $50 doesn't go very far unfortunately.
I'll give a few options that a beginner cyclist may not have.
- Bottles and bottle cages: You can go much further on the bike and in more comfort when you have a way to carry water.
- Tub of energy drink: Most new cyclists do not have a well developed aerobic engine and end up 'in the red' on most inclines in the road/trail. Energy drink can help keep you going stronger for longer and have an more enjoyable ride.
- Saddle bag + spares: Conveineint way to carry the basic tools/spares to get you going again after a minor mechanical mishap
- Good shorts: Look for some $100 shorts that have been discounted to $50.
- Good tyres: Over your budget, but for me the best upgrade you can make to a bike. Add an additional $50 and get some high quality tyres.
Look at your loadout - what situations have you got into where lacking a tool/spare/part was the difference between getting rolling again, vs a phonecall of shame to ask for a pickup.
Example I broke one tyre lever recently, trying to change a flat. Now I have two much-better ones on that bike, plus the surviving spare.
I've also been stranded by not having a pump that fitted my tyre valves. I'd assumed the pump did both presta and schrader, and I did not have the little $1 adapter. Pump was schrader, valves were presta, and with no adapter I couldn't even use a service station air pump.
If you're riding and notice that some part of your clothing is remiss, then consider that. If your gloves are worn with holes in them, replace. If you ride longer distances, say over 30 km on a regular basis, then padded shorts may help alleviate any saddle pains. Hand pain may show you need better/thicker grips.
If you ride at night or areas with poor visibility/width, a lighting upgrade is a good idea. A daytime rear light can be used all day for added "see me!" safety.
If you just have to spend it, then spare tubes are good to have on hand.
Otherwise save it for a rainy day when you really do need something.
Road bike: $50CAD bought me a used hollowtech crankset that saved me a whole pound over the old square taper setup. I ended up selling the old ones for $30 anyways, so it was a really cheap upgrade.
Mountain bike: Everything on that bike is either way under or way over $50, but my XTR shifter comes closest after factoring in selling the old ones (yes, plural, I fixed up a free shifter and sold it for profit). Massive improvement in shift quality, and those carbon levers look fantastic.
The question is a bit vague and depends really on the kind of bike, and the "level" of the bike, and most importantly, how dedicated you are. But I would say:
- safety: high visibility clothing, helmets,lighting if riding in low light situations, helmets,
- clothing: short, wind blocker jacket
- tooling (on the go): multitool, spare tubes, pump, saddle/frame bag, ... for long rides
- tooling (workshop): foot pump with a manometer is a must
- bike rack at home
- commuter bikes/utility bike: mirror (totally underappreciated, I recommend those which are attached to in the handlebar's end, others can be too flimsy), puncture resistant tires, fenders, rack, foot, anti-theft wheel fastener (for instance, some require the bike to be horizontal to unmount the wheel)
- comfort: saddle, ergonomic grips, pedals (on city bikes, they might be very slippery)
- gadgets: good phone holder (for navigation)
Definitely puncture proof tires
True, a pair top-of-the-line puncture proof tires (Schwalbe Marathon Plus) cost a bit more than 50$, but it's worth every cent, imho. It's the difference between having a flat every 100 to 500km (depends on the roads you are riding) and having a flat maybe in 10000km. That's a lot of cursing you save yourself, simply by riding robust tires.
There are other puncture proof brands out there, and they strike different balances between price, robustness, and rolling resistance. Afaik, the Marathon Plus is the best in terms of puncture resistance, so other brands are likely better in price and rolling resistance. But I cannot give evaluations on those because my top priority is not to get flats. As such, I've stuck with the Marathon Plus ever since I tried it first.
By far, the best $50 was purchasing accessories for a drop bar.
Long time ago, as a poor student, I bought a new hybrid bike that actually worked for 500 EUR (before it I only had bikes my parents paid for that didn't even work, probably costing around 100-200 EUR) and started to ride it a lot on paved roads -- so much that it could have been argued the bicycle was too cheap for its job and the type of the bike (hybrid bike) was not optimal.
I became aware that high quality bicycles for on-the-road use had three features: (1) clipless pedals, (2) high performance narrow slick tires, (3) drop bars. Buying (1) and (2) were easy and I considered them to be meaningful improvements to my bike.
However, (3) drop bars was a problem. All the information I had about drop bar conversions was that drop bars were something that should have been on the bike originally and that if one wants a drop bar bike, one should buy a drop bar bike. The problem with this is that the bikes with drop bars had prices starting from 1000 EUR and had problems related to utility: no kickstand, no possibility even to install a kickstand, no fenders, no clearance to mount fenders, no eyelets to mount fenders, no eyelets to mount rear rack, too short chainstay to use panniers (they'll hit your legs), no hub dynamo, no lights (the "solution" seems to be battery lights which I hate), no reflectors (although they could of course be added later), no room to fit studded winter tires, etc. So paying 1000 EUR to buy an utterly useless new drop bar bike didn't seem to make any sense, especially given that I was a really poor student and even the 500 EUR bike was a major purchase for me.
Not knowing whether I like drop bars, I started to search for an abandoned drop bar bike. In the campus area where I lived, abandoned bikes were annually distributed freely. Knowing that 30 years ago drop bars were fashionable, I could perhaps find a used drop bar bike to see whether I like drop bars. Unfortunately, I only found a really poor quality bike. The frame was heavy gas pipe steel and spaced to 6-speed freewheel hubs. The wheels were out of true and there were broken spokes. The rims were not double wall. The brakes were centerpull. All bearings were practically seized and to make matters worse, the bottom bracket used an obsolete standard so finding new parts to overhaul it would not have been realistic. So the only part I found I might use from the abandoned bike was the drop bar. It wasn't even realistic to test ride the thing once to see if I like drop bars.
So I thought: why not convert my existing hybrid bike (with suspension fork) to drop bars? I bought Dia Compe V-brake levers for drop bars and Shimano Ultegra 8-speed bar-end shifters. I think the cost for both of these was probably somewhere around $50, perhaps bit more, something like $60-$70.
Then one day I started the conversion work. The installation was easy, because the drop bar I found happened to use 25.4mm mount that my stem had and not 26.0mm or 31.8mm mount (31.8mm was not even invented back then when the salvaged drop bar was made). I test-rode the bike and I enjoyed it a lot. Because the bike frame was originally made for an upright riding position, the fit wasn't that problematic: only a couple of centimeters too long. I rode the bike for 4 and half years with the drop bar. It was the strangest thing ever: the only drop bar bike I have ever seen with a suspension fork!
Later, I decided drop bar was my thing and as I earned more salary, I bought a Surly Long Haul Trucker frameset and started to accumulate components for building it into a bike.
Most are above the budget, especially in a pair, but not all of them. Arguably, I am not that familiar with US prices (or were they other $s?). It also depends on the bike category. MTB very much differs from gravel or road.
This will strongly change the wsy how your bike rides and will add better puncture protection than puncture-proof tyres can get you and without the inherent performance penalty they would bring.