PvP is another great matchup that requires excellent unit control and sound macro-management.
Usually in PvP people start off with pylon, gate, assimilator, gate, core. The reason why you want to go for this double gate build instead of making a nexus right away is that if you do a really early fast expand then mass adepts will be extremely difficult to fight off. Adepts have the ability to shade, so they can be in one place and then teleport to another. Trying to fend off this attack with a limited amount of army supply is going to end up with you having a ton of dead workers.
After you do get your gates up and start producing stalkers or adepts (and usually stalkers) then you can expand and go into your tech. Robo is a pretty solid opening because it allows you to get disrupter or colossus tech, and immortals are also pretty nice, but oracle and dt tech are also viable it’s just a bit of a gamble because if you don’t do any damage you will be behind.
Early on you want to aim for a stalker / sentry / immortal composition. Adepts aren’t really that great as you go into the midgame but they do have their uses early on because they are such a powerful harass unit and great for scouting also. Sentries can provide your troops with guardian shield and force-fields can really turn the tide of an engagement and stalkers are just an all round good unit to have. You will eventually need to research blink so eventually twilight council will be important but templar tech isn’t really a thing in PvP except for making archons.
You will need to stay on top of your chronoboosts and avoid any unnecessary buildup of nexus energy. Another fun and sneaky move is to take a ninja base early on, especially if there is a gold base on the map, and then recall a bunch of probes to this base so your opponent can’t see the workers being transferred. Getting your gold online asap can mean a massive economic advantage but if your opponent scouts this tactic you better be prepared to defend two places at once.
Aside from getting that killer stalker / colossus / sentry / immortal composition you will want to keep an eye out for prism harass and potentially do some of this yourself. A quick warp in of charge lots or adepts can wreck havoc in your mineral line if you aren’t careful, especially later on when the protoss player has so many warp gates to use for the warp ins.
Observers are important, not only in order to prevent devastating damage from dark templars, but also just for general scouting purposes and keeping tabs on your opponent’s troop movements. You can also use a single zealot or adept for this purpose, sending them across the map and gathering information. Information is power and you always want to be aware of what your opponent is doing and when he is moving across the map so you can adapt accordingly.
Staying on top of top of your upgrades is very important. Colossi are useless without extended thermal lance so you will want to get that one and blink right away, as well as warp gate of course. But attack and armor upgrades are vital. A few shield batteries can be useful in helping you hold off vulnerable expansions and they are very cheap to invest in.
When it comes to engaging ranged units vs ranged units you want to get a good angle for your attack and if you can establish a concave then that is very beneficial. Usually the defender will have an advantage, not only because their reinforcements arrive so much quicker (although if you have a warp prism this isn’t really a factor because you can warp in reinforcements at the battle as well) but also because the attacker has to move in to attack and this puts them somewhat out of position. Microing away from disrupter hits, either with blink or even just sending a sacrificial unit to take the hit is also good.
It is possible to tech up the golden armada, and the mothership itself is pretty valuable in any late game PvP but carriers just take so much time to produce. Of course if you do go for carriers you will want to make sure that you max out the air upgrades as well as the shield upgrade from the forge. During the late game you do want to make your army as strong as possible. That means upping your immortal and archon count and just getting an absolutely high tech high vespean army if you can afford it. A few sentries are still great to have later on because when you have such a massive battle going on adding a modest amount of armor is extremely worthwhile.
Zealot run-bys are a great way to do some economic damage without much risk, especially if you start to build up a massive mineral bank because you have been going for these high tech units in order to make the most efficient and deadly composition possible.
Strategic recalls can be useful, either to save a base or if you think your troops are going to be in trouble and you need to regroup and beef up your army. Your units are still vulnerable for a while after they recall so it won’t save you if your forces are totally routed but if you are about to get trapped but haven’t quite yet then you can get away. With the new patch changes recall is almost always an option especially during the mid and late game when you will have extra energy built up.
Make sure that you do choose your engagements wisely and don’t be afraid to make a tactical retreat if it looks like you won’t have a profitable fight. Sometimes discretion really is the better part of valor.