Well, there are several things that should be kept in mind during this level. First, the green ally is rather stupid and you need to keep an eye on his base since freakers can easily take it off. He can defend with your help, but if he is dead you are also dead and very soon. Second, you don't need much of a defence here and it's better to attack since the enemy buildings in the north-west corner are poorly protected with only one rotary tower. Even if your attacking force is not that strong, you can always take off a couple of buildings and waste some of the enemy's RUs. Third, everything should be done very rapidly, because the RUs are rather limited; the game should take no more than 40 minutes. Fourth, the wasp bombers are very dangerous! Try to scatter the troops as much as you can to minimize the losses.
So, at the very beginning move quickly to the southern exit from the green base, turn a little bit north and move the outpost to a narrow passage in the north-western direction from the green rig. Build the outpost in the middle of the passage. Immediately build a Research Lab and Machine Shop to the north of your outpost. Start producing a derrik and upgrading until you can get snipers. Meanwhile, send pickups and bikers to help the green oil rig defence and ATVs, tanks and snipers to the north-western bridge.
When the derrick is ready send it to the north-eastern patch and build two power plants, one close to the rig and another to the south-west. Upgrade the Machine Shop and build two more tankers and a derrick and send them to another rig to the west. Start building snipers, but don't make too many because they would be eventually destroyed by the wasp bomber. Try to scatter your troops all over the territory until you can get 40 or 50 snipers. When you group these snipers, you don't have to be afraid of anything.