Definitely get the Bilsteins first. That way you can fit a larger tire.
Check out the leveled section of the forum HERE
. You'll find tons of information and pictures about what fits and what doesn't and what your set up will look like.
With the Bilsteins set at max you will be able to fit full 35x12.5's but using your stock rims will limit you on that. With an aftermarket rim it will work no problem (provided you get the correct offset). With stock rims you can fit a 35x12.5 on with 1/4" wheel spacers. The problem is that Nitto Trail Grapplers actually measure 13.5" wide.... that's where you'll have problems. Personally I'd wait until you can get rims and tires at the same time. You'll end up with a nicer set up and save money in the long run by buying a package deal. If you want some pricing on wheel/tire packages email the guys at Bully's Performance at email@example.com
. Be sure to mention that you're a forum member and they'll hook you up with great pricing on everything you need.
If you want to stick with the stock rims and put bigger tires you can run up to a 285 wide tire with no spacers... typically anything wider will require 1/4" wheel spacers. Lots of guys run 295/60/20's when they're leveled.... again, you'll see a lot of that looking through the threads in the leveled section.