The 4 gate has become one of the most used Protoss openings, due to its balance and effectiveness. The main idea is to wall off with a gateway and a cybernetics core to prevent early rushes. This will give you time to get your macro going and get 4 gateways (made into warpgates) to build up a sizable force.
* 9 – Pylon
* 12 – Gateway (at ramp)
* 14 – Assimilator
* 16 – Pylon
* 18 – Cybernetics Core (to finish walling off ramp)
* 18 – 2nd Assimilator
* 21 – Stalker (chrono burst)
* 21 – Warpgate Research (chrono burst it constantly)
* 24 – Pylon
* 25 – Gateway
* 27 – Sentry (you want one early so it can start building energy)
* 30 – 2 more Gateways
* 30 – Use Probe to plant Proxy pylon
* 31 – Stalker
After you have your warpgates, produce a mix of sentries, zealots and stalkers at your proxy pylon. If your rush fails to defeat your opponent, progress into the late game as usual. Happy hunting!