It is important that when you are in combat that you keep an eye on the 'Attack' button for when it flashes. When it does flash tap it to automatically unleash 'Special Attacks' and spells.
Hand Tips
It is worth asking around when mastering a different skill as plenty of NPCs give you hand tips that will help you.
Help
Remember to tap on other players to open up 'Chat' and 'Party' options whenever you need help taking on bigger foes.
Power Boosts
Dressing your character in Cosplay Items can also give you power boosts.