A Rosy Boa is a great Choice for beginners. They are fairly small but the females get up to around 3 feet I think. They come in lots of great colors. Don't have high humidity requirements. Most of them are very tame from the beginning of tame down in a couple days. The nice thing about Rosies is that they are slow moving so novice handlers don't have to worry so much about it getting away.
Whatever you choose, please read up a lot on the internet and in any books you can find. Research research research. You can never know too much about an animal before you bring it home.
Good luck with your choice and Welcome to sSnakeSs