As for the printer, ender3 and ender5 are good budget buys, if you add a ABL sensor it's as good as prusa if not better while I'd argue my ender5 prints better than my prusa.

Here is the filament extruder I built:

https://medium.com/endless-filament/make-your-filament-at-ho...

You might find this interesting as many people end up spending thousands of dollars in filament and lots of wasted printed parts as getting accurate part takes several attempts.