Your teams shouldn`t be based on types.
Here, I`ll give you some examples :
- Pokemon who are bigger or longer than 3m
- Pokemon who look similar to animals (like Houndoom = dog, Miltank = cow, Tauros = bull, etc.)
- Trios (you can choose 6 of those ones : Articuno, Zapdos, Moltres, Raikou, Entei, Suicune, Registeel, Regice, Regirock, Uxie, Mesprit, Azelf)
- Eeveelution gym (Pokemon who evolve from Eevee) - I guess you`ll like that one most :)