I'd say it really depends on what kind of riding you're after. If you're happy with its current power, then get rid of those Bridgestones and stock suspension! TheDog is right, get rid of the air injection and open up the carbs and exhaust a bit, you should be able to do that fairly cheap. I had a long term goal with mine, now my motor puts down 80+ hp at the tire. But it gets spendy. There are a lot of options available, read up and decide how far you want to go.

Always remember to be yourself. Unless you suck. Then pretend to be someone else.