It's always hard to decide, i guess go for what you can afford and like. Lizards are pretty cool as they have character and are fun to watch. However, I don't think you can go wrong with any type of reptile as it's all a learning curve and a fun one at that. Good luck.
Not set limit really, I probably don't want to pay more then $400-$500 for any one specimen. I only am working casual at the moment, but would rather say 3-5 herps then a single woma or something.