Gah! Do SOMETHING, hair!

Blasted curly/straight/wavy/frizzy hair! >.<

I'm at a loss with what to do with it.
I have been using an organic shampoo/conditioner and tend to let it dry on its own. It always comes out frizzy.
Now, I'm totally clueless what to do style-wise. I have no bangs and tend to tuck it behind my ears, letting the edges fluff out behind me. After a few days it tames down a bit, but particularly after washing, it's frizzy and unmanagable!

I'm tired of looking like a 15 year old, and am ready to look more adult and professional (hoping to get a good job) but still interesting. I have a straightening iron, but after just a few days, my hair starts to feel and look greasy.

I've been looking on the web for styles and haven't found anything that I think I can manage on a daily basis.
These days I'm either putting it in a ponytail or halfway up, but thanks to the frizz, I get little whispy flyaway hairs that make me look... well, let's just say slightly insane. =P

I've never really been big into hairstyling and makeup and that sort of thing and now at 23 I'm trying to learn. Any suggestions?
Pictures? Help!