I'm idiotically using Black, Trunks and Yamcha. Once I could get some meter and actually get a good string going with Trunks I'm not too bad with him. I need to seriously do more training with some other characters since Frieza and Cell seem quite interesting. I'm shit with 18 though.
That's not a bad team at all. Yamcha seems like a great anchor. From my perspective you might need a "battery" character like Gotenks, Goku, or 18 that can do lots of meterless damage and help Trunks get that meter but the game's so new that I don't know if that's really necessary at this point.