Exit beacon on bottom, go to Barracks to become Marine, go around killing Zergs for money... go to Armory to buy a Skill Point when you have enough Minerals so you can get the Alpha Ghost or Beta Ghost.
A bug messed up several other units' stats, so just stick with Barracks units.
The only item of real value is the Skill Point; other items are not really complete in the version above, though I'm working on it.
Play the map with a few friends, it's actually pretty fun, with functions like Overthrow

. (psst, you need all the players except the guy you're overthrowing on the beacon for it to work)