New 54 Gal Corner Tank

[FrankieS1026]

I have had this tank for a few months but feel I need more equipment. The tank wasn't drilled for a sump so I am at a standstill when it comes to that. I have an aquatop canister filter, and heater at this point. What else am I missing and what is the first thing I should buy. I know a protein skimmer is down the road but I am also not sure of which one to get.

Currently a FOWLR tank (niger trigger and dwarf lion) and some snails and hermits.