Welcome aboard!
Nothing wrong with feeling that your skills aren't great. That's what drives us! Even the seasoned pros look at their own work and only see ways to improve. Like everything, you get better with practice, and play. If you're just starting out, don't ever be afraid to make something that "sucks" or just a mess to play with the tools and experiment. I myself do a ton of just mucking about and experimenting without a goal in mind, just to get the ole' neural circuitry active.
If you're just starting out, and trying to get some control and have a bit of fun, I'd recommend getting some kid's coloring books and coloring them with your airbrush. Don't worry about trying to stay in the lines to start, just get comfortable throwing paint and seeing how your brush responds with different things, and playing with color. As you get more comfortable with that, slowly start to pull the trigger back less and tightening up your lines.
Also, try breaking out your pencil and ruler and an exacto knife and cut some shapes out of paper and spray through them.
You'll be shocked at how quickly you start to pick things up.
When you are ready, talk to people on the forum about exercises they do to improve, from dots and lines to dagger strokes and textures, there are tons of techniques and tricks that any one of us is willing to share.
Above all, make it fun, and never be ashamed of what you've tried.
Every one of us here started from the same place, so we're happy to pass on what we learned.
It's a great forum full of great advice and amazing artists that enjoy helping out their fellow airbrushers.
