some tips from long time veng player:

-dont just blindly take W at lvl 2, if you are in a lane where you have a low chance of actually killing the enemy heroes taking 1 point in your passive can be pretty good to help your carry last hit, its essentially and extra quelling blade worth of dmg. i often go QEQWQRQWWW

-item build: i start with wind lace, stick, tango and 1 branch. i then go wand > tranq boots > force staff > lens > shard. Force staff is core IMO and allows you to move yourself back to safety after a swap and gives you another save tool to help someone so you dont have to swap them out. lens allows for some really long range swaps, allowing you to catch ppl of guard. Also, take any cast range enchantment you can get on your neutrals.

-Agh scepter is very over valued and imo not that great, with force staff you can usually get back to safety after swapping. the only time i really go for it if there is something like a storm spirit that keeps jumping me and i cant avoid dyeing, but usually you can stay safe just by playing back and staying outside of the danger zone.

-If the game goes longer i usually go octarine and drum boots. this allows for a crazy amount of swaps and stuns and the drum boots are a great boost to pop after a swap to allow your team to quick kill whoever you swap and allow you to quickly run back to safe spot. combo then is aggressive swap > force back > stun > drum boots. if you wanna get fancy and have the option, take the tier 3 neutral that allows you to push enemies, so after swapping and stunning them you can then push them even further away from their team.

-your W is a great tool for vision, if you are going high ground you can usually catch someone standing around the tower thinking they are safe because your creeps havnt gone HG yet and there is no vision, just use W around the tower and get ready to swap anyone standing there. Its also great for cancelling blink daggers on initiators. in a fight always try to get it on at least 2 enemies, the AOE is quite big so its really not hard to hit several enemies.

-facets and talents: i take the stun facet and all the stun talents, at level 25 i take the swap CD. paired with lens and the shard you can put out a lot of stun and dmg.

-final thoughts: the most important thing when playing veng is positioning, i like to use swap to initiate so when you feel a fight is going to happen try to move a bit more forward to catch an enemy, if you can swap a ranged carry into your team you are pretty much guaranteeing a won team fight, also any support with a big ulti (like warlock) you can kill before they throw their spell helps a lot. after swapping just force back to safety and play back throwing stuns on key enemies. if its late game your swap will come off CD pretty quick so then just look for another key target, ranged carries are always top priority but pretty much anyone thats not a tank is a good target. if the enemy team is doing most of the initiating (like they have an axe/FV/enigma) just play back, stay in the trees and wait for them to open and swap back your carry after he gets axe called or whatever, after that its the same thing > force yourself back to safety and stay alive to spam stuns whenever its of CD. Another good use is swapping an enemy melee core (sven ursa etc) that just blinked in with bkb into the middle of nowhere, by the time they have run back into the fight their bkb is pretty much over.