Spectate? It is a double track day for $125 or something. For that price, you could run every other session and still have a great time. Leave the boost low, and get on track and actually enjoy the car. As a minimum, bum as many rides as you can during the day - watching cars on track is boring if you aren't driving (or riding at a minimum).
As far as rain, it is fun in the rain; but it can be pretty un-nerving if the track isn't wide open with tons of run off.
While it sounds great to say, buy the right tires and just go crazy; it isn't that simple since that requires spare wheels (other than just your standard track wheels/tires) and also thinking ahead. Plus, most guys drive to/from the track; so stuffing your car into a berm/tire wall/etc comes more into play. So most good drivers concentrate on good, clean lines and car control.
Josh