16" is perfect for a hat. I agree with Ingrid that it's far better for the stitches to be bunched up than stretched out.
I use 16" circs for hats and switch to either magic loop or two circs when the top gets too small for a 16".
Knitting is like anything else, it takes time and practice to learn to do it right. The important thing is to just relax, enjoy it, and keep going. Don't worry too much if it comes out perfect, just get it done. You'll learn a little more from each one and eventually it'll seem easy to you.
Trust me, when I first started it all seemed extremely difficult to me and now I design my own sweaters. Ok, they're ugly sweaters, but they're still mine :rofl: