I am looking to ride with strava, however as a teenager I receive very little to no money regularly and I do not have a smart phone. I would like a device that tracks my ride via gps and exports a gpx file so I may upload it to strava. It must cost less than $100 AUD.
It's a little more than 100$, but you could have a Garmin Edge 20 for 130$. Maybe wait a little for a special or something*. According to the post it's a good little computer and I personnaly enjoy using their Edge lineup.
(* the website has a 10% anything coupon with their partner, might be worth a look, that would bring the Edge 20 to 117$, might not work for everything thought)
Instead of an actual GPS device, I would recommend buying a used smart phone, (The Strava app itself only works on either iPhones or Androids). A "Nothing Special" used smart phone you can usually find for maybe 40 bucks, depending on the model and brand.
Download the app and just take the phone with you wherever you ride. It's not a fancy system, but it works. This is the method I use now.
I'm surprised that nobody suggested to use an inexpensive hiking GPS, such as a Garmin eTrex 10 (US$ 89.99) or eTrex H (many available on popular online auction sites for US$ 50 or less). They have the same high-accuracy GPS chip that more-expensive GPS devices use, and they have excellent battery life: 20 hours on a pair of AAs.
The downside is that uploading to Strava is more complicated; a cable and a computer are required. I use the computer program GPSBabel to download from the GPS and output a GPX file, which can then be uploaded to Strava. GPSBabel can be a pain to learn how to use, but it can upload or download from nearly any GPS device, and it can input or output nearly any GPS file format. There are many other programs that can also do the job, including free software from Garmin for those running Windows.
I'll grant that a second-hand smart phone running the Strava app is easier to use, but an inexpensive hiking GPS is water-resistant, a lot more rugged than a mobile phone, and can also be used for backpacking. (Always remember that a GPS is a backup to a map and compass when backpacking.)
I picked up a cheap android phone wiht a cracked/broken screen for $5. No sim or cellular service is required to get GPS service, and I don't care if it gets dropped.
A USB battery might help if the internal is weak or small.... without battery the little 1500 mAh phones run strava for about 4 hours.