To get combos, attack with weapons and spells of the same property.
For example, have a caster use an elemental spell such as one of the
fire ones that attack one opponent. Then, make sure a character is
equipped with an elemental weapon such as a sword or knuckle with the
same type. You can usually tell what type an item is by the name or
by the resistance it gives. For example, fire resistance for a fire
weapon. If you use both attacks at the same time, it has a random
chance for the two characters to do a single attack, which does five
to six times the damage compared to the non-combo regular damage.
This works best on Bosses.
Turn the battle speed to maximum, and turn off battle animations.
This will make most fights that usually last a few minutes end in
about ten seconds. Only do this if you are quite strong and do not
really care about strategy, but want to save time.