Sigh-Fi

Tires last a very long time. Tubes can be repaired over and over with patch kits. Chain lubrication helps keep the things running longer, but you can go a long time without lubricating your chain, and if you ever do need to lubricate it, you don't really need the specialized bike-specific oil, just any light machine oil.

A typical bike emergency repair kit fits in a small pouch under the seat or inside the frame.

There are some specialty tools you need if you are doing advanced bike maintenance, but I do most of my own repairs and I've never used half the tools in my lunchbox-sized tool kit. I know how to use a chain whip, but I've never actually needed one. I've never needed a bottom bracket tool or a crank puller. For the most part, the tools you need for bike maintenance can be found in basically any toolbox.