One-base play vs zerg is less common than forge fast expand (FFE) but is viable in the current metagame. This option opens for a quick +1 Zealot timing attack (possibly including Charge) followed by a Reaver drop, which can be devastating to an unprepared zerg player. This build must inflict damage, otherwise a greedy zerg will be far ahead in economy.
One such build is:
ElBowser's 1 Gate Stargate into Expo 3 Gate - Build
14 Cyber Core
18 Nexus Upgrade
After that when Resources allow:
- Stargate (when finished Sentinal)
- Twilight Council (when finished Zealotlegs)
- Second Zealot (situationally a third one)
- Another Pylon
2 General Options:
- Add 2 Gates first and then the Nexus
- Build the Nexus first and then 2 more Gates
2 General Stargate Options:
- Build 3 Sentinals for ground support and add Corsairs later or when needed
- Build 1 Sentinal to scout and commence to build Corsairs immediately
Round out with (no specific order):
- Templar archives
- Robo + observatory
- 3 Gateways
- Third Nexus
You want to wall off in your main, if you face a speedling-all in you might want to consider adding a pylon to make it a full wall off and building a dragoon instead of a second zealot to defend from behind your wall. I usually scout after building my gate, but I think that that is up to personal preference. Also I usually chronoboost my sentinel twice and then instantly send it to scout my opponent. Furthermore, against any number of lings that is greater than four you want to go up to at least 3 zealots (one to guard the wall off and two to secure your natural vs the lings) before you build your Nexus, assuming you went Nexus before extra Gates.
Nexus or Gates first:
Gates first provide pressure and/or punish greedy builds. If you commit heavily this can kill a 3 hatch before pool player almost always. Do keep in mind that adding 2 gates before the nexus and not getting anything done with them gets you quite far behind economically though.
The other variation is more macro-focused, but you need to be really careful with it. Although you have a stargate it is really fragile and it is more or less impossible to hold off a hydra bust. Scout carefully when opening like this, because getting caught off-guard can lead to frustrating losses.
The two variations here are really easy to understand. One counters muta play, and the other is good vs ground unit based play. With 3 sentinels you will not only have absolutely amazing pressure potential but you will also have great harassing options. Seeing as you only build zealots and sentinels then though you will have a rough time if mutas suddenly show up.
Opening with only one sentinel it´s main purpose is to scout for you. You can delay this decision for after your first sentinel scout. If your opponent took two gas and went to lair quickly he is likely to go mutas and you should go with the Corsair focused build. If your opponent took quick 3 bases you most likely don´t really want to spend your resources on 6 Corsairs though. Scouting is key in your decision what to make out of the Stargate, interpret your opponents moves correctly and you will almost always get a lot of benefit from having the Stargate.
I usually start my natural wall with a forge. Starting +1 attack is really important for a Protoss as it makes your zealots just sooo much better. Also try to keep chrono boosting upgrades as much as you can in general. The order of the rest of my building depends a lot on what I scout. When the opponent went mutas you want to chrono as many corsair out as you can, and don´t really need a robo and an observatory yet. If your opponent went for quick Lurkers you want to rush for exactly that though. In general it is also never a bad idea to allow yourself the luxury of a cannon at the front and in each mineral line.
In general I also warn you from taking your third too quickly. I would advise you to almost never take your third without having added another 3 Gates, if you do that, you are playing with fire and can easily die. Against ground based compositions you also want a rather quick storm addition into your army. Taking a third vs a ling/hydra player with 3 Gates and no storm in your pocket is suicide in my opinion (I´d love to you to prove me wrong though).