StarCraft/Protoss mission 5: Choosing Sides

Establishing Island Defenses
Your starting location is pretty convenient—a good-sized island with very defensible cliffs and lots of resources. You can actually complete this mission using only the resources of your base and the rest of your island, but more likely than not you will have to expand to one or both of the additional resource nodes, which are located on different islands and defended lightly.

First off, though, you need some solid defenses to stem the tide of Zerg airdrops while you build up a force. Photon Cannons are your best bet here: they detect burrowed units and have longer range than Dragoons. After you have a decent number of Probes going, have one build Cannons all along the southern and eastern edge of your island (not just the plateau that you start on), adding more as you get more minerals. It might seem a bit wasteful, but having lots of Photon Cannons will eventually save you units and time.

As you're pumping some initial Zealots and Dragoons, expand to the northeast part of your island. There's a huge mineral deposit here, plus a Vespene geyser that you can build a lot closer to than the one in your initial base. Build Photon Cannons here as well; the Zerg most likely won't attack this area, but there's another threat that might. More on this later.

Of course, you will need to climb the tech tree. Build two Forges, an additional Gateway to speed up unit production, a Robotics Facility plus the Support Bay, and a Stargate. The Citadel of Adun and the Templar Archives are optional, but it is strongly recommended that you build both. You won't have much need for High Templar in this mission, but Archons will come in extremely handy later on. Plus, those Zealots can always use the leg enhancements.