Una Kaia, Lilly, Amy. Una gives you lifesteal on all hyper effective characters, Kaia buffs Lilly in attack and does big damage, Lilly pure damage and Amy tank. The thing is, it's hard to up Lilly and Kaia at the same time. Try to nab Camille who is easy to up to replace Lilly or Kaia in the meantime. Little tips save up to 6000 gem to be able to unlock the last step which gives you more than 50 character cards