JetPens has good guides:
From this list, I can personally vouch for the Platinum Preppy and Pilot Metropolitan. Though the Preppy is a disposable, the catridges from the non-disposable Platinum pens fit it. You could could even get an eyedropper and refill the cartridge from a bottle of ink.
https://www.jetpens.com/blog/great-beginner-fountain-pens-th...
Most of my collection is in the under $20 range, most under $2.50 and the worst I've had is the ink had dried, which took some soaking in water for a bit to get out, but this was from letting a pen sit unused for months.