yup, height and weight really determine the board size. Personally I just started last year and the first time I rented for $25 just to make sure it was something I was going to enjoy before I started spending some serious $$ for equipment. Renting will give you a good starting point before you go buy, sizing, binding style, normal/goofy (which foot is forward), etc.
I’d also look for a used board/bindings setup to start, I’m riding an older board that was barely used. It came with bindings that got me through the season, but I’ve since upgraded for this year. The only piece that I would suggest buying new would be boots.