First turns Research and builds.

[Arkcon]

Against the AI, do physics twice, then get phased polaron beams. Phased shields are a long way away, and you will slice through their ships once you have it. Meantime, defend your planets with DUC's and CSM platforms. And by being nice to the AI while you research.

When you're on the ropes because the AI is coming on too strong, quickly research Construction, then Mines, and plant a minefield on any warp point or around a small planet the AI will go for. Once the A.I. is hit by mines, it will pause its construction and research to research mines itself, so it can have mine sweepers. Don't take a nap here, use the pause to build something that will tip the power balance in your favor -- like troops to capture a nice planet of theirs.

Oh, and be prepared to abandon all of this when you play against humans.