As odd as it sounds I feel like working on your own bike is reason for N+1 bikes...it's a lot less stressful to work on a bike when you know you have another that works. I started with 1 bike and was reluctant to do anything other than lube the chain. I would take it to my LBS for everything else, but that legit adds up fast. As you do and learn more there's some key tools to get: Good lower torque Torque Wrench 2-12Nm give or take this is key for adjusting handlebars, seatposts etc to make sure you don't overdo it Grease - generally speaking unless it's the actually chain/brakes grease is your friend for threads and other moving parts Bike Stand - plenty of cheap portable options, will make life much easier than flipping stand upside down Cassette Tool - most are the same and used in a number of different places, add a chain whip to the mix to make sure you can remove it Thumb Nut Drivers ( https://a.co/d/05tuygFy ) amazing for dealing with water bottle cage nuts etc General Tools - I'm a fan of Harbor Freight in many cases a few specifics....'meme tool' is great for smaller spaces, a good set of metric Allen wrenches (icon and t handle can both be great), if you do bigger things a higher torque wrench is needed for bottom brackets and cassettes (40Nm ish)
