Nothing too special here. Just your typical Trinity/Atmog build and the way I'd do it with Riven. I tried it out on my first time playing her and it worked out wonderfully. Basically stole this build off of what I used with Lee Sin.

Boots are always something you can change according to the enemy. If they lack any substantial CC, you can get away with CDR boots or boots of swiftness.

You might also want to get the sheen earlier in the build to help with your burst damage. Completely up to you. This is simply how I've done it.

At the end you can even sell your lantern for a blood-thirster for more damage while keeping your life steal, or you can replace it with a GA for more survivability.

EDIT: 2nd build is a different way I wanted to try. This build will give you more survivability early game from the health regen which also helps build into your Warmog. I also wanted to get some key damage items earlier. Let me know what you think.