I have a 2007 FZ6. When I bought it I went overboard and bought alot of stuff for it. I should have purschased a few of those items first and stuck to a budget. Here is food for thought:
1. Frame Sliders installed by the "DEALER". For about $85 or less you can have them installed and save yourself from major damage to your front fairing, mirrors, handlebars, and engine case. Think of it as insurance.
2. A K&N airfilter ($35). It is like putting a "breathe right strip" on a 100 meter dash sprinter.
3. A 12vdc waterproof cigarette lighter receptacle installed off of the bottom left hand corner of the handle bar mount. For about $59 installed you can have power supplied for quick and easy use of any commercial GPS, radar detector, or cell phone charger. The dealer wired mine in such a way that electriciy is only present to the receptacle when the bike is turned on.
These three suggestions should make your bike more prepared for an accidental spill, perform a little better, and be more convenient.
If you have the dough, this is the order I would follow for additional items.
4. Adhesive tank pad placed at the gas tank near your crotch. This item is positioned to avoid belt buckles, jacket snaps, etc. from scatching your tank at that location. approx $15 or less on the internet and you can put this on yourself.
5. LED turn signals. they are not expensive and illuminate brighter than stock providing a greater chance for oncoming and behind traffic to recognize that you are about to turn.
If you want performance mods that give you the biggest bang for your buck, by a pair of used exhaust pipes such as stainless steel Scorpion's. The have them in carbon fiber etc. Yes, I said used. They are mechanical sections of pipe and instead of buying them brand new for $400 + you can often get them half-price or cheaper off of ebay or some place like that. To link your addition of a K & N filter and high flow exhaust I would recommend the installation of a power commander. This will run you a bit of $ approx 300 but their is a noticeable improvement in performance. This combination will set your bike apart in a crowd just by the "growl" it makes and the subsequent heads it turns going down the road.
If you want to make your bike look more like a street racer (R6 or R1) look at TCP Aerodynamics website. They sell after market body plastic additions.
Good luck, don't take your eyes off the road and hold on past 6Krpm!