If you have 2 Taps then you will need
1 Co2 tank
1 Co2 regulator
gas line ( 1/4 or 5/16 is fine)
a splitter for the gas line( to go to 2 kegs)
2 ball lock gas disconnects( I prefer mfl flare fitting with 1/4 barb fitting screwed on, it makes it easier to disconnect for cleaning than the Regular barb fitting disconnect)
2 ball lock beer disconnects ( with same connectors as above)
3/16 beer line and clamps for all hose fittings
not sure if you have shanks, faucets and tailpeices, but if you don't you will need then as well