hello this is my first time doing a build guide.... Either way i just wanted to show how i play riven. Half tank major dps, as the title says this is a 3v3 build not a 5v5 i go the same build in 5v5 just without the latern.

so i hope you like my build :)

Runes i pick amor penetrations runes for marks armor runes for seal and magic resist for glyph because it gives a great benefit in early game you can push your opponent out of exp range pretty hard with these runes

i go a 21/3/6 for the extra armor in early game and the extra exp from utility, and the offensiveness in rivens play style gets really good benefit from extra armor and extra exp

i go for latern as first item because when you have build it you around lvl 5 - 7 then you can solo dragon and give your team and nice sum of money, then frozen mallet for the HP and for the slow effect so you dont lose your target when they run from your awsomeness.
atmas is a good choice after because it gives you a good amount of extra AD while still being alil defensive, War'mog after for getting a full effect out of atmas, if you play against someone like garen or tryndmere i would take thornmail instead of war'mog so that they attack 30% on them selves.
phantom dancer is a good combo with frozen mallet so that you get even more hits on them before their teammates get to help.
blood thirster is to give the last PAW effect it's not really my favorite chocie i go between infinte edge and blood thirster both can be good but blood thirster can be very risky and can even get useless

i take broken wing first for first blood ganks because it makes it hard for melees to hit you and it can be used to stun your opponents totake the first kill home.
then ki burst for the stun and because it have the best extra damage from AD.
valor goes in on lvl 4 so that you can run if your enemys decides to gank you and it would have been a waste of their time.
for blade of the exiled i only got 1 comment, and its because i've seen many rivens do it and it really stupid, blade of the exiled's shock wave is NOT for damage its for finishing enemys off when they try to run if you use it as dmg they will run asap and you will loose 1 or 2 kills on that account so wait with the shock wave to AFTER they start running.

Flash and Ignite is a known combo its no suprice that its good, flash is mostly for a quick get away, but ignite got many actions which to get the opponent down, for instance fighting against tryndmere put your Blade of the Exile on to max out your damage and DONT use shock wave, when tryndmere then use endless rage keep fighting for 2 seconds and then pop ignite when he runs shock him and ignite well take the rest if he got any hp left.
ignite can also be used when you focus a target like akali because when she pop her sphere just use broken wing and when she shows from an attack use ignite and boom akali is doomed
ignite can also be good for jungle, when you solo dragon at lvl 5 pop ignite for extra damage so that you sure to take the kill hom because els its kinda risky because you rely totally on latern and it does not pop ever attack so have a potion with you.

at lvl 5 riven should go for dragon when fighting dragon go in with valor as first spell the ki burst and broken wing (remeber to let a normal attack between spells for passiv effect) after you have used valor use a potion for health dragon hits hard and if you use potion to late you might die, remeber to pop valor or els dragon takes your hp away pretty quick so you die faster and making the enemy aware of you trying to take dragon.
when dragon is gon go directly for the non buffing creeps in top jungle for getting your hp up alil from the life steal in latern and remeber to engage every jungle fight with valor for the shield, when you got the 2 buffs from top go down and take red buff, red buff is alil risky because you got big chances of getting countered and lose the buff and give the enemy team a kill, but if it works then go gank right after because your team should have higher lvl than your opponent and should be easy for riven to gank any ap, just rush in ( at a good time ofc.) with valor broken wing to get ot your target Blade of the exlie and ki burst, and ignite if you have it

this build makes you very very hard to kill when you first got atmas because you will be the main dps on your team and it makes you able to solo dragon from lvl 5 which gives you good amount of extra gold if you take dragon every time he's up