Helo, Painting is something you just have to dive into and practice.
Depending on what type of models you build can determine what technique works best for you.
I myself build mostly armor so painting does not have to be a pristine affair as it would be in autos or
aircraft.
You also might want to look into using cheap water based acrylics such as craft
paints instead of expensive
"modeling paints" that's all I use and I feel the end results are good.
Painting figures especially can be very frustrating even with my 40 odd years of modeling my figures
generally suck, that's why I avoid them like the plague.
Don't get discouraged, after all modeling should be an enjoyable hobby and a distraction from the tedium
of everyday life. Keeping your mind sharp and giving you a challenge to learn and achieve something new
can work wonders on one's psyche.
You will improve with time and soon you will begin to be satisfied with your results.
I myself am a brush painter and never used an airbrush but many swear by them and achieve excellent results.
You may want to try them out and they are not prohibitively priced.
Good luck to you in your future endeavors and don't hesitate to ask for help or advice as all on this site
are very kind and always willing to help.
Jim.