Well, you could do an offensive starter, such as Blaziken or Infernape for fire. Then you could put supporters or defensive starters like Blastoise and Venusaur. You could do a combo like Emboar, Sceptile, and Blastoise. You have your heavy, powerful attacker, your quick, physical or special attacker, and your supporter/defensive starter. These are just ideas. I mostly agree with what JirachiCelebiMew said, you can use any combo, but those are more specific ones I thought would be good.