Pros:
Fun
Mobile
LOTS OF DMG
1v1s

Cons:
You wont have many friends if you play this champ
Has to SHUTDOWN tanks early
Countered by hard CC
If behind hard to get back in the game
NEEDS KILLS to be useful

Fast Combo: This Usually works better if the target isnt moving

AA+Q+Click back (repeat until Q goes on CD)

Harass: I used this when I am against harder matchups
3Q+W+E(away) or just W+E away

Burst+ Engaging in Teamfight

E+R+Flash+Hydra+W+A+R2(2nd R)+Q (If im against alot of CC i usually use the Q to leave if I am not I usually stay in the middle of the enemy team for the follow up from my team.)

1v1: This is very dependent on what the enemy champion does but this one is the basic.

E+R+Q+AA+Q+AA+Hydra+W+Q3+R2

Riven is one of the best SNOWBALL CHAMPS. Only defeated by the snowball god himself NUNU.

Riven needs the early game kills. If she doesnt get any she is USELESS. This is why passive-baiters and champs with a good built in sustain are super effective against riven.

Try to kill your laning opponent early but, if you are against a hard matchup try to roam more.

Assuming if you are doing good in lane. Roam and help your team with mid ganks and TP bots.

However if you are not doing so great. Make sure to KILL STEAL and only go after squishy champs. You may have to adjust your builds and give up some good items but it should be worth it.

This is where tanks become UNKILLABLE.

During a late game teamfight make sure to sneak up or flash to the enemy back line and dive them.
Make sure your team has their CC when you go in.
However even though you have ALOT of dmg you are short ranged so dont be stupid and E+FASTCOMBO into the enemy adc with them knowing.

SHE IS SUPER EASY TO PLAY!

No she is not! At a high level of play canceling her animations and knowing when to go in a team fight is difficult. Just spamming your Q is not gonna win you your lane and the game.

ALL RIVEN MAINS ARE TOXIC!

This honestly a stupid stereotype. Most GOOD riven mains are actually chill. Only lower ranked riven players are usually toxic since you know... they are bronze?

OMG RIVEN NO COUNTERS OP NERF!

Riven's is only "GOOD" because she is basically building AD+CDR. However buidling AD+CDR is honestly THE ONLY WAY riven can even be USEFUL. This is why riven is a glass cannon. Top lane is usually an island for tanks.FARMING SIMULATORS, ARMOR STACKING, TANKS. She needs to shutdown a tank early on or she will get outscaled and be USELESS.
BUT SHE CAN ROAM?? Roaming is also risky. You gave the enemy toplaner free time alone just for a CHANCE to get a gank mid or TP bot.