Join Date: May 2007
Location: Wasilla, Alaska
Probably a lot of advice on what accessories (farkles) to get for your bike will be that the best ones for you are the ones that best fit your needs/desires/pocketbook. If I were to recommend one absolutely necessary accessory, it would be a center stand, right off the bat.
Good ones to have include a auxiliary fuse block, EB headlight relay, heated handgrips for cold weather riding, a better, aftermarket windshield, an aftermarket seat if the stock seat just doesn't agree with you. You indicated that yours is an adventure model, so you already have some pretty good options that come with the bike, however, as good as the suspension is (improved over the '04--'11 suspension) some will advocate doing an upgrade, but only you will be able to tell if you need better than stock.
Pretty much, it's hard to know what you'll want from the start, but as time goes by and you put more time on the bike, it will become apparent to you what you will need. There are tons of aftermarket accessories out there from many different sources, so you will need to shop around.