My commute is about 25km/day. I have a cheapish hybrid bike with Shimano gears, v-brakes and SPD pedals. I carry a small hand pump and spare tube.
What do I need in a bike tool/ multitool or other spares?
A multitool basically only needs to include the Allen wrenches that fit your bike, plus screwdrivers to fit screws on the bike. It doesn't hurt if the tool purports to include a tire lever, but I wouldn't rely on one in a multitool to be any good -- you should carry regular levers or a Quick Stick if you intend to be prepared to repair a tire.
The jobs will dictate the need of tools. Look at the hardware you have, and what needs to be turned to perform common repairs and adjustments:
Allen Wrenches for the size bolts you have. Tire Levers. Potentially a small screwdriver bit, depending on the hard ware on your bike. Lugs for wheels if you don't have quick releases.
The question is similar to asking what is necessary to cook without knowing what the dish is. Sometimes you need an oven, sometimes a grill, sometimes just a mixing bowl.