Here's how I've set up XP2 filters from bottom basket to top.
Use filter pads and/or foam pads in the bottom basket, fill the top basket with ceramic rings, bio stars, or seachem matrix with an optional filter pad or fine filter pad on top.
Theres really no need for carbon but if you want to have some type of chemical filtration then may I suggest Seachem's Purigen the initial cost is a little more expensive than carbon but youll save $ in the long run because its rechargeable and reusable.
You can fill the top basket half way with rings, stars, or matrix then place the bag of purigen on top with an optional filter pad.