you don't have to buy boots before, it's optional. I didn't and never had any problems with breaking them in during basic. i never had any blisters either. there is a transition period where you will be alternating between boots and tennis shoes to getting your feet and boots used to it. And if you buy your boots ahead of time, that's over $100 that you spent, or you can wait for a few months and just be issued them. you want to take as little stuff to Basic as you can, because you will be running all over with it, carrying it in your left hand, along with the other ton of stuff they issue that day. Everything can get real heavy, real fast. I showed up with the bare minimum, which is pretty much just paperwork and whatever personal items you need (hygine stuff).
Orientation is not mandatory. You get to spend the first day doing briefings about the Academy, then you go spend the night and next day with a cadet. it is here when a lot of people decide if the Academy is the right place for them or not. I already knew it was for me because I did a tour my sophomore year, and Summer Seminar Junior year. I would highly recommend orientation even if you have been to the Academy before, because you get to meet a lot of upperclassmen, and see how the Academy works after Recognition. this is important because if you want to "look" at the chapel or fountains or mountains or anything besides the person in front of you, go to orientation, or you will get busted during Basic for gazing.