One of the first things I added to my bike (after the initial bare minimum utility stuff) was a water bottle cage. $8 for the cage. Each of my three water bottles is a 50 cent bottle of Trader Joe's water. I refill them and reuse them. Even on a 6 mile ride, I may go through 1.5L of water, so I often have to refill while I'm out. The grocery store I use has a water fountain across the street, and a public restroom where you can refill water bottles. Most of the local parks have water fountains too. It's reasonable to be thirsty in when exercising or in hot weather. Both at once will have a major effect.

I'm ok with spending money on a snack when I'm out riding. But I do have a budget for snacks and treats, so I don't want to blow it. I'm trying to get into the habit of making myself a sandwich or burrito to take with, so I don't end up caught short while I'm out. One memorable time when I tried to push through "hungry" I ended up toppling off the bike in slow motion.

Most of the rest of staying in budget is prioritizing. I want to be able to haul things like dining room chairs, wood for an end table, and donations for the local thrift shop. That means I need either a bike rack or a cargo trailer (haven't quite decided which is best). And well, a trailer is Not Cheap. Nor is a good bike rack. Most of my other wants will cost less, but they don't do as much either.