First off i want to say that i just started today so dont expect much. i get kos with it on people higher then me. (even a level 60 who was training not that it matters =-p) but i want to know how to improve it. Also i m mostly a collector. so mostly i jus buy the first new card i see in market
First you need to focus on a clan or two. I suggest going for a pure Rescue to give you an easy start.
In Urban-Rival clan bonus is important once you have learned through experience you can try moving on to other clans. Also get cards with power 5 or greater.