How should i restock my tank?

ok so i went on a 8 day vacation so i bought a vacation feeder thing. the fish wouldnt eat it so all my swordtail and platies died but my zebra danio and blk neon tetra and my oto all lived. its a 20 gallon with a oto 4 zebra danio and 3 blk neon tetra now. the other fish died and there bellies got eten by the others. i wand a rainbo shark in it definately but i lso want a couple more fish. maybe neon tettra or 2 dwarg gouramis or a cory. any ides?