Place melee units with a one square range in front, followed by long range units. Put the longest ranged units at the far end. Behind them, position another line of melee units in the event that the forward lines are taken out and back them up with more ranged units. Only send your hero into battle when they are required.
Defense
Maximize your slots in defense as soon as possible to repel attackers. Consider using a row of melee vehicles, followed by machine gunners and mortar men. Then place a row of riflemen backed up by grenadiers. If you can avoid getting attacked, you will not lose any resources. Players usually avoid attacking well protected bases in order to minimize troop loss and the time it takes to train replacements.
Free spins
Each Boss battle in campaign mode rewards you a number of free spins. They will give you a chance to win equipment, diamonds, and other rewards. Play those missions until you exhaust all your spins.
Gems
Gems are needed used to upgrade your troops. Do not spend Gems to upgrade troops, such as Grenadiers, that are used infrequently. You can randomly get Gems as a random reward by completing the Boss levels in every single player campaign mission. You can play each of them five times per day to farm gems. Gems may also be picked up as a daily log in reward, free spin award, and Treasure Box item. They also may appear after leveling up or completing certain missions. The easiest way to obtain Gems is to complete single player campaign missions with a three star rank in all stages.
The Arena
Early in the game, you can find easy battles against poorly defended bases. Consider getting wins that result in the largest rewards. Win in the arena first, and spend money on upgrades to prevent their loss while you are logged out. After you are unable to attack other players, begin the single player campaign.
Upgrades
Upgrade your Flags as soon as possible. They will determine the size of your army. The larger your possible population, the bigger your army and the better you can defend your base and defeat your opponents. After Flags, upgrading your troops should be your priority, followed by the Air Base Planes, the Defense Center, Barracks, and all other buildings.
