I own a Storm but many of the buggies benefit from the same upgrades. Not sure if your diffs come greased or with diff oil. My Storm came with grease and upgrading to diff oil made all the difference on the track. As far as weights go, they vary. They make them any where from 1000 weight all the way up to
100,000 and everything in between. I run 5000 up front, 7000 in the middle, and 1000 in the rear. Your choice of tires will depend on the surfaces you run on. Many of the guys in here have multiple sets but there are some all-around chioces that are good on most surfaces. Check out Panther tire and Proline. I'm running the stock metal geared servos that came with my buggy and I'll keep them until they fail. A popular brand of servos I hear alot about is HITEC. Something you should do before anything else is do a search in the forums. Chances are someone else who has a Hyper 7 has already asked the same question. Not that you won't get a response because someone else already asked it, it might be faster if you do the surfing, see what's already been said. Keep this in mind. Just because there is an upgrade for a particular part on your buggy doesn't mean it's necessarily better.
I have a Titanium chassis, but my wheels are still made of plastic. My point being, that Titanium wheels (although stronger than plastic), might not be a good upgrade.
Pick and choose what's best for you, do your homework. Good luck and have fun.