"Some are born to ride beater bikes. Other’s have beater bikes thrust upon them."
Living in an RV, the only place to store a bike is on the rack out back. So, no nice fancy bike for me. I currently have a cheap WalMart bike I managed to find during the bike shortage because someone had returned it. The gears it came with made the bike unridable.
The first thing I replaced were the front gears. I went from two chain rings, 38 and 48, to three, 22-32-42. Much more usable gears.
Next it was the tires. I was getting a flat a week. I broke down and bought a pair of Schwalbe Marathons. So far, 600 flat-free miles.
Recently the bottom bracket committed suicide. The exact replacement cost $17. A sealed unit that will last thousands of miles and is much smoother cost $21. I went with the better one.
Next step is replacing the wheel rims that just won’t stay true. I saw some nice DT-Swiss cyclocross rims for $45 a piece. Maybe they’ll be cheaper after Christmas.
Then better brakes, a new seat, peddles, etc.
I once built my dream bike this way. One piece at a time bought off eBay and yard sales. It turned out to be exactly the bike I wanted. Unfortunately, it was not the bike I needed. It was too much the racing bike and not enough a commuter bike.