This is what i have in my tank 14g Biocube (i sort of modified my tank a little also) and it becoming a reef tank (slowly). 20lbs of ls about 17lbs of lr in the tank and then in the back (filter) i took out the carbon/foam insert and just put foam, took out the bioballsa and put some denitrate (lr rubble is better but i had a nitrate problem) and in the third chamber i took out the foam insert and put a bag of carbon. you will also need a clean up crew (CUC), i have a numerous snails: trochus, turbo, nass. Hermits: Scarlet, and zebra reef. And i will probably get bashed for this but i also have 1SMALL sand sifting starfish.
the one thing that is most important is to take it very slow.
cycle the tank before you put anything in it and then slowly add like one fish and maybe a couple snails or hermits as you need them (if you start getting algea then you need them or if you seed food laying around for very long)
and use RO water
that is just what i have and have done, hopefuly it helps you out but please read as much as you can on this forum and whatevery you deside to go with just ask questions about it
you need to be well informed in this hobby