Sump for 33Gal

[Maverick00]

Hello Canreef! not only am i new to the forums, im new to the whole aquarium set up to begin with. Im currently running a 33gal tank, heater, 2 pumps for water movement, and skimmer. Contents in the tank are 6 chromis, 4 hermit crab and some weird red eyed crab i got with the 39lbs of live rock. Id like to build a sump to hide the skimmer and heater, what size of sump would be recommended for the size of tank and does anyone know a good sump 101 article? thanks in advance.