You can always switch one Armour quint out and throw in a AD quint.

Farming is really easy with riven. Just last hit everything early game. Try to average at least 60-70 farm when it hits 10 mins. Once you get hydra you melt minions waves.

Once you get a black cleaver and titanic hydra it will be just like the regular bursty Riven mid game. Late game when there's starts to be team fights you can do one of two things:
1. You can sit back and peel for your adc.
2. When you get tanky your actually able to be on the front lines ( this doesn't mean just run into a 1v3)

Riven works really well with champs like Gragas, Elise, ammumu, Rel Sai, lee sin. Always try and have good communication and things like ganks should work out well.

Riven has Crazy out play potential
Can 2v1 easy
Alot of Mobilty
Able to Be on the front line.
Riven Has a good amount of cc alone
you still have alot of dmg
alot of fun

Hard getting used to
Cant go crazy like the other riven builds