I had an E46 323i. Good car. I changed oil and control arm bushings - that's it. Decently sporty.

Dump the X5. It's stupid to even consider keeping that truck if you don't have finances to back it up. It will break and it will cost you considerable money sooner or later. In the meantime, it will drain your gas fund.

Buy anything Honda if you have little money for gas or repairs. I've owned three Civics, great cars and run forever.