It really depends on where you ride and when. Also what you plan to do with it. If you ride alot in the rain I'd say windshield, otherwise tires. I will send you a PM about windshields.
Everyone seems to love the toolbox.Wind shield first.
If you ride in the rain a lot, I'd recommend the Yamaha tool box.
I've ridden through some heavy rain, dusty environments, and sand....it keeps EVERYTHING out. It's great for storing sweaters or anything you want to keep out of the elements. I thought it would be useless but it's one of most useful accessories that I've spent money on.