I enjoyed the tutorial videos by The Adipose after I had already started on an adventure of discovery about strategies for my own game. I'm now playing four different teams, and have found one I really like: a red-yellow-black team.
I have chosen red at this point from a purely character-driven perspective, unfortunately. I'm not a fan of Matt Smith and so have not watched much of the 11th Doctor; so 10th Doctor's red ability sets the stage. He is also a powerful healer and currently the only one on my team. I have paired him with Jenny for her conversion ability and because I've determined every color should be paired.
My yellows are Amy Pond (tank) and Madame Vastra (who may have started as a tank, but I've leveled up her atk as well--she's a beast!). My black team is Porridge and K-9 who work very well together with their stun and bomb abilities. I am mowing through every enemy I face with these guys!
Who do you like? Why are you using them?