As riven I build the zephyr because it gives you cd reduction attack speed and damage but then I build life steal/damage but this guy told me, "I should be building way more AS" and at level 18 I have 1.47 AS and I don't see why I need much more because I would build a phantom dancer but I don't think Riven with crits is that great

Riven scales with AD and CDR.
Attack speed won't do as much DPS as an AD/CDR build.

That guy is a scrub. Riven is nearly a Physical Caster, with all her stuff scaling off of AD. When played properly she gets in 1 autoattack inbetween each Q cast to use her Charges to deal maximum damage.

Getting lots of AD and armor penetration will do a lot more than attack speed...especially now that AS is nerfed and AD is cheaper.

Rivens not a auto attacker... your rely more on your abilities. You combo...combo again.. cooldowns are not long and the few autos you do between cooldowns don't warrant buying a AS item.

AS is useless on Riven. Including the Zephyr, by the way.

If you're doing more than the occasional auto for her passive charges, you're doing it wrong.

I cant say its optimal, but that doesn't mean it cant work. Try going into Dom and trying out the build a few times. I've built AS Vi and done alright. I basically use her abilities to initiate, get in some more AA, and then chase the same way I initiate. Not really the best way to play her, but it can still be a lot of fun haha

Attack speed isn't useless, but its definitely shouldn't be a priority on a riven. As its been said, her abilities scale off AD and are the primary source of her damage output.