With all due respect, this is a tech support forum. If you want to start doing reviews it's not very likely that you'll have companies queueing up to give you expensive gadgets for free. Best way to get started, buy them yourself, review them, build a reputation and then maybe, MAYBE you can get freebies. B ut I wouldn't hold my breath, I'm sure there are thousands of high school and college students trying to do exactly the same thing.
If you want help in shooting and uploading your video to youtube, and maybe some recommendations in iPad video editing apps, folks here may help you. but since this is a user to user tech support forum, there's not much folks here can do for you.