The easiest place that I know of to find such files is Odysee. Search for AWCY (Are We Cool Yet) and Deterrence Dispensed. And search for people showing off 3d printed guns. They will sometimes include tips for printing.

As far as printers go, don't cheap out. Things like auto-bed-levelling and a direct-drive extruder are really helpful. Maker's Muse on Youtube is a great resource for 3d printers in general.