Im laning as cho vs riven

Cloth and 5, max your E first.

Try not to die level 1, get your Q level 2 to counter her hard engage, level E level 3, level W 4, continue maxing E. Your Q and W are there to peel for you, don't spam them, just save them and time them to negate Riven's damage. Good positioning with your E can both help you last hit beyond your reach, which helps you scale and utilize your passive sustain, and help you harass Riven, which can turn one of her engages around if you play correctly.

I would personally start Doran's Ring + 2 pots. Start E. Take Q second. Max E.

9-21-0, magic or hybrid pen marks, attack speed quints, armor seals, and scaling mr glyphs (if zero ap threats take scaling ap or cdr glyphs)

Cho's E on hit steroid is crazy strong, ranged area of effect damage with no mana costs. It is quite honestly superior to rely on E for damage so you can focus on using W and Q mostly for disruption. If you take E level 1 you can shove the lane easily and if she ever tries to wack you near your minions just disrupt and hit her back. You have far better sustain until she has a BT or Hydra and both of those heavily delay her armor pen.

Whatever happens it is imperative you focus on last hitting for recovery, with E ranked up it's very very easy.

There may be situations where the ranged poke/burst of leveling Q or W might work, especially W for the increased silence (may be good in this Riven matchup). E is crazy strong though. If your damage is tied to a 9 or 12 second cooldown and part of your CC you're either trading damage output or safety...

My build path is typically double doran's + cloth armor into sorc's shoes then Zhonyas. Don't really need RoA. I might pick up a thornmail after Zhonyas. Hue. Or more AP is good. With full feast stacks and defense masteries you are reasonably tanky.

Dorans ring and max your silence. You want dorans for the mana regen and AP. You don't need cloth because Riven has a hard time all inning you as chogath. You want Riven to be standing there without abilities for as long as possible. If she jumps to you just silence and walk away. If she continues chasing just drop your Q on her while she's silenced (so she can't dodge it). She takes a huge chunk of damage from minions and your ability and you get away scott free. Post 6 you should be able to get a very easy kill with feast.

I recommend RoA against her as a first buy. Riven doesn't deal well with tons of HP. Armor is nice but it doesn't help as much against her execute as flat HP, and cho gets a LOT of flat hp between his feast stacks and RoA.

tbh i'd probably either start cloth 5 or flask, riven can be a huge lane bully but cho has better sustain and can just silence or knock her up if she tries to run up and beat you up and if you try to trade, make sure your minion wave is bigger than hers early minion dmg is cray

Maybe ive been doing it wrong but usually if the opponent doesnt have crazy sustain I just max my Q and simply poke them down with it untill I have a big HP advantage. Trying to avoid melee trades.