This is a great model marine supplies video, check it out-
A 3 Barracks opening that I like to use. Build order is posted below. Numbers represent your supply at which you make that unit/building. Numbers assume no units lost. Numbers may be slightly off, just worry about doing them in order as quickly as possible. 10 Supply Depot 12 Barracks 14 Supply Depot (Finish Wall-in… every map is different) 15 Refinery 16 Scout 17 Marine 17 Orbital Command 17 Tech Lab (First Barracks) 17 Supply Depot 18 2nd Barracks 18 Marauder 20 3rd Barracks 20 Supply Depot 24 Reactor on 2nd Barracks 26 Supply Depot MAKE SUPPLY DEPOTS NONSTOP WITH 1 SCV 27 Tech Lab on 3rd Barracks CONSTANTLY MAKE 2X MARINES AND 2X MARAUDERS FROM ALL BARRACKS. 35 2nd Refinery PUSH OUT ONCE FIRST MARAUDER SPAWNS FROM 3RD BARRACKS 45 Stimpack Constantly produce units. Depending on how our attack goes: Goes Well: Keep pressure up, producing units If Goes Normal: Tech to Medvacs If Goes Poorly: Turtle and build Command Center in main to expand. Hope this helps 
