I've been there every year. General admission is a good choice for the first time as it will allow you to check out several spots. There's good viewing around T5&6 and T7,8 &9 from spectator mounds. The reserved grandstands for the most part are covered which can be nice depending on the weather.
Oh, and don't forget ear plugs! The MotoGP bikes are deafening, like nothing you've ever heard.