start off with a longsword and 2 pots. on your trip back get vampric, then get boots because vampric helps keep you health up when you need more health. Then you want to go into building a blood thirster after getting in the entire recipe following into a black cleaver. depeding on you situation, you would either build last whisper, mallet, mercurial, thornmail, or even guardian angel.

As a riven it isn't always best to engage with triple q all at once. You have to understand the mechanics of her moves and use it to your advantage. its best to hit your q once, hit twice, and then come back for your final q. I usually do Q, Q, E(into them or out depending on the situation, and come back and Q and W and AA(auto attack) between every Q to get maximum damage while engaging the enemy. Then, when enemy is low or tries to come back to CS(creep score) AKA killing creeps, I am able to zone them a bit out of range so that they are not able to get any experience from the dying creeps.