Beta is exactly that, a beta, it's for massive amounts of people to find issues, for instance, the Danish Superliga last year changed to a different format, and the game didn't award prize money after it changed. If you're looking at starting a long-term save, it's not for you. I definitely try to help make FM the best product it can be, and just try to break the game in beta.
As for buying 17, it's really a personal choice, if you're still enjoying 16, it's probably better to wait for sales and get it then, if you're like me where you feel like you've done just about what you wanted to do 17 might be a good leap right now. Unless you want to do bug reports, the beta really isn't important to get in to.
EDIT:
IT'S HAPPENING