Male boas stay much smaller than females. I would definitely get at BCI, or dwarf boa to start with; although, dwarf boas are quite a bit more expensive. Most BCI's have great temperaments, but do have a really good feeding response, so make sure you are careful while feeding. Most also do not mind to be handled often.

Make sure you are prepared to properly care for a boa. If so then I suggest getting a salmon boa. You can get them for a great price, and they are really nice looking.

Hope this helps, and good luck.