Ive recently been addicted to this build. I had been using the typical 4 gate opening when playing however I was encountering a problem of when to stop building units and expand. It was also difficult to choose what to transition into. I like grabbing a Twilight Council for Charge however, as I have discovered, having an army consisting mainly of Zealots and Stalkers will get you no where fast if your opponent is grabbing some higher tech.
I started opting for a Robotics Facility instead of a 4th Gateway, this opened up a wide range of possibilities. I can now get a substantial army out quickly and be able to fend off early Stalker, Roach, or Marauders. I usually go for 3 gateway units and 1 Immortal to start off, but this is a quick drain on my resources and 1 base is not enough to support the constant production of said units. So when the gateways are ready for another round, I quickly warp in 3 more and grab an Observer. I should have barely enough for another Immortal and 2-3 Gateway units and then I stop producing and begin expanding. If I don't have enough or I am getting some constant pressure from my enemy, I will keep making Warp Gate units, but only those units, this allows my money reserve to fill so I don't have to stop unit production to Expand.
My unit composition tends to be an equal mix of Zealots and Stalkers and maybe a sentry to use my Warp Gate charge. Early on Zealots are nothing more than meat shields and against Terrans they can absorb a lot of that Marauder and Marine fire.
Now for the next step, applying pressure. I do this for two reasons:
1. I need to expand, what better time than poking into there base?
2. I need to see what unit composition they have.
If they are going for mostly marines, I need to warp in more zealots and drop a Twilight Council down and grab Charge. This will also open up High Templars, which eat Marines for Lunch, or teching into Robo Bay for Colossus. If they go Mass Vikings or Mutas? Warp in some stalkers. Heavy Marauder push? More Immortals.
Once the expansion is down I grab the 2 gas geysers. From this point on, Protoss are very gas heavy so having that extra gas will be useful, if not immediately, then later on. I then transfer probes and begin warping in and training more units. Getting another 3 Gateways, Teching up or dropping a Forge down to get some upgrades going. All these are viable options. The forge is more important as now that you can produce more units and having them deal more damage and take less is super valuable. Just make sure that all your resources are going into producing more units and Pylons as at this point, you will probably have more minerals than you know what to do with.
This build helps me keep a relatively safe position while feeling safe to expand, and I am able to get units up fast while steadily moving up the tech tree.
I have several problems I am curious to know how to handle properly. Early Aggression and when to expand. With the way I'm doing it now, I can get the expansion up around 70 food. Is this too much? I know a lot of people expand around 50, but I feel a little vulnerable. I bet if I tried to make an earlier push, I wouldn't feel so vulnerable.
The most important factor in all this? Play with a real person in some practice matches. You learn more from 1 game against a human than you do in 10 games against the AI.