What is a good entry level mountain bike?

[fortheworld]

I'm about 5'2", 120lbs. I just moved to Montana and started getting into mountain biking. I'm looking for advice on a good quality but inexpensive bike. I don't know if I need suspension, But I know I need disk brakes. Do I need a women specific? Should I buy used? I'm not sure what else I should be looking for. I want to spend under $500. Any suggestions on brands, where to buy, what to look for, brands deff not to get. . . will be appreciated.