Injustice help


Fairly new to fighting games, was hoping to get some Injustice advice.
My main two are batman and Green Arrow.
With Batman, my best combo relies on meter air grapple, wall bounce, meter air batarang, etc. 10 hits 30%
Green arrow, using combos with ice arrows, wall bounce, meter air exploding arrow, etc. 9 hits 30%
I’m starting to see how combos can be linked with specials, but I seem to be using a lot of meter, and I know these characters can do much more damage.
How can I take my game to the next level? What technique am I missing? I have videos of the combos I can post if it is of assistance. Thanks for the help.