I have never used tobacco carts, but here's what I've tried and liked:
Chocolate is good with any of his chocolate juices (german choc. cake, choc. macadamia nut), and cherry bomb makes a chocolatey cherry vape.
Vanilla is my 'catch-all' carto, because I can put whatever juice in it and it's good.
Dr. Pepper is good with either dr. pepper juice or cherry bomb.
Cola is good with either cherry coke, vanilla coke, or cherry bomb.
Cherry cartomizer is good with pomegranate juice
RY4 is good with anything, I think.
RedBull cartos are good with red bull drops.
I have about uh...30 or so little bottles of juice, but really only tend to order the above cartos and mix and match.