1) The best mod for the money is to upgrade the suspension front/rear.
2) If it doesn't already have one, a Power Commander unit is recommended to allow proper air/fuel rations across the board. as opposed to the OEM lean settings.
3) The OEM final ratio (16/40) is very high, so a front/rear sprocket change to a ration along the lines of 15/41 to 43 (or mathematical equivalent) allows the engine to rev fully, and save the clutch on starts.
4) Depending on your use (track, street, combined track/street), tires can be subjective.
If you primarily ride the bike on the street at less than 9/10ths, sport/touring tires can be a better price/performance ratio. They are quite good these days, with most being multi-compound long wearing centers and softer sides.