As in the traditonal Pokemon games the key to winning battles is to have a balanced team. When you improve your team look to add versatile Pokemon with special abilities, purple/blue/gold moves, and a solid white attack..
Defense
On defense select a Pokemon with a movement of 2 or above in order to quickly place them on or near your goal. Then place your second defensive Pokemon on the left or right side of one of the Entry Points as maintaining control of these is as important as protecting the goal because if your opponent manages to place an enemy on top of one of your Entry Points you will be unable to place more Pokemon on the board on that side.
Offense
On offense you will want to have two Pokemon that have a wheel that is comprised of one solid white or gold attack, a 2-3 star purple attack, or a blue defensive move. The smaller their miss ratio is the better, this can be reduced if need be by leveling them up using the Fusion mechanic to expand an attack or ability, thereby reducing the rate of misses.
Runners
It is important that you have two solid runners which although may not be the most offensive/defensive Pokemon they are aggressive enough to push forward and reach your opponent’s goal. Ideally these Pokemon should have a well-rounded batch of stats that will enable them to clear enemies out of the way, disable them, or simply use up their turn.