Happy to help
As far as a paint gun goes you really don't need expensive stuff. H.F. has a nice gravity feed non HVLP gun pretty cheap. HVLP is very nice, but it takes a bunch of compressor volume (not pressure) and most small compressors just wont keep up (6.5 cfm or so) so stay with a reg. gravity feed gun. Do your body work first and get it as slick and feathered as you can before you put on primer. If you prime with a urethane primer you should be OK for a while with out top coating. Urethane (or 2K primers as they are often called) do a nice job of sealing and filling so you don't get much shrink or die back. Again just be sure and follow the manufacturers directions (even on your filler) and you should be OK. When you get the gun pick up some cheap paint of some type (even hardware store enamel) and practice getting the reducer right. Years ago when I first started I painted some mailboxes, little red wagons, old bicycles and stuff for friends to get some good practice. Sometimes I even got paid for this. Not much but it helped pay for my practice paint. Just get your adjustments and gun technique down before you start on important stuff. DO NOT be afraid to put down some paint and always remember anything you screw up can be fixed. Good luck and if I can help just let me know.