1. Get your metal mine to at least 3.
2. Upgrade all other buildings to 1 at least. Upgrade to barracks as well.
3. Upgrade to the resource converter 2 so your oil can be turned into metal.
4. Choose a building category. Focus on upgrading to the Ion Cannon, Missile Silo, Shield Generator, Resource Convert level 5, or the highest metal mine. If you want to play aggressively, upgrade your farm to level 2 so you can build outposts.
Thats a good way to play, and you can improvise from there.