Welcome to the forum! Sounds like you're in for some fun. If I were you, I'd look at as many pics as I could to decide which body style you prefer. After that, get on the hunt. Like the previous guys have said, 70 and 71's are the most popular and most expensive. The 72 - 74's are more reasonable. The major differences in the years are grills, tail panels, and engine sizes (the big blocks were gone after 71). When you find a car you are interested in getting, post pics of it here and we can give you honest opinions about price, how much work it will take, etc.
Glad to have you on board!