This is my tactic, I swear by it.
Using Anders I build
Three supply pads
Reactor
Barracks
Build three Spartans, then upgrade supply pads.
Using the Spartans go rebel killing, upgrade to fortress and build another two supply pads. Upgrade reactor and then take a second base.
On the second base build a reactor and two vehicle depots, build three cobras and upgrade their first ability. Put the Spartans in the cobras and build five wolverines, upgrade to fortress and put two supply pads, air pad and a field armoury.