Ride it as it is and keep looking. Maybe set a limit of what you might spend to get it just a little more ride friendly. I have bought bikes for 10 bucks and put 300 more into them but I was starting with something that really fit me and was of high quality just neglected. You can get a small frame to work but it will fight you every step of the way and when you are done it won’t be perfect just ok. Don’t stop riding while looking but this is the perfect time of the year for used bikes. Keep your eye on CL and garage sales and when you see the right one run don’t walk because they don’t last long. If the bike you have just needs a cable or a new seat you can swap out to a different bike later fix that but major gearing changes with the plan to use them later on another frame I don’t think I would do. I have many times taken 3 or 4 donor bikes and made one good one and maybe one ok one to give away. If your labor is zero that type project can be fun.