As you play through the game you will need to build holograms they start out as weak ones that have very little strength and don't last too long. Soon though you would be able to build stronger ones that will be able to last longer to give you more time to defeat Vexos Bakugan and defend your land mark, which is recommended in later battles.
Holograms are very important in the game, they help draw attacks away from your landmark that you are trying to defend. The Key to a good holograms is building on that is strong against your opponents attribute so that it will take longer for them to destroy it.
Later in the game there will be times you will have to build 2 or 3 holograms and you go against opponents of 2 different attributes in that case just split up the strengths of your holograms so that at least one will be tougher to take down.
During one of the early to later battles you will come across Vexos Crystals that will be able to use Bakugan Traps over and over again, once you defeat the traps they just send out new ones. To stop this the first thing you must do is destroy the Vexos Crystal that is producing the traps so that you can win the battle without the worry of Bakugan Traps popping up and getting in your way.