She's definitely my second favorite champion in my adventures of 12 levels (behind Cho'gath). However, I feel like I do no damage with her. I mean, she's not overly complicated, and I think I understand her mechanics. Ill tumble into a condemn, but it barely scratches anyones health. And Ive been using a mobafire guide on what items to buy.

Any help? What am I missing?

Shes' an AD Carry, and as such scales exceptionally well off of items. Early game your damage output won't be all that high.

As for items... While her W (and AD steroid) does make it so she values AS slightly higher than other AD Carries, you still are going to be dealing most of your damage with auto attacks. Think of W as a nice bonus, not as your primary damage source (because that's what it is, a bonus).

So how should I view Condemn? I'm looking at it as her hard hitting ability, when it really doesnt. I resorted to maneuvering with tumble to make use of condemns stun.

Condemn is either a stun if you can get it off for additional damage (free auto attacks while they can't retaliate), knockback to keep them away or interrupt them, or a last ditch attempt to finish them off before you give up the chase.

You aren't really looking for the damage out of it, it's utility with a bit of damage as a bonus, not the other way around.

Oh okay. Thank you. So is an attack speed build viable for vayne? Since you said most of her damage comes from auto attacks? Well like a mix between attack speed and attack damage

Even with her W, you still want to get damage first, because of how well her tumble scales with attack damage, and the fact that you're simply going to be doing straight up more damage with your auto attacks rather than the procs.

sword of the divine, infinity edge, bloodthirster, phantom dancer, black cleaver, berserker greaves, blade of the ruined king, guardian angel, mercurial scimitar, and last whisper are all good picks for your standard AD carry (which vayne is).

the greaves, bloodthirster, and infinity edge are the only ones i would say you "must" get (and either phantom dancer or sword of the divine). the rest goes up to personal preference and the way the game is going. there are other items as well that could get on the list depending on preference/what's necessary.

I've only played her against bots, but I've been going Attack speed first.

Health potions and boots to start, and additional potions as necessary.
AS Boots, then a Vampiric Scepter for sustain.
I move into a Phantom Dancer.
Then a BF sword to either continue a Bloodthirster, or start an Infinity Edge.
Most of the time I don't get the Infinity Edge built.

The attack speed from the Phantom Dancer helps with kill securing, and the critical makes it actually hurt; not to mention that you can now roll through a group of minions.

What I find is that I have to chip away at enemies at first, especially the bruisers.
Generally, hit, hit, Q, hit for true damage, back off.
Unless I catch them between me and a wall, and then they definitely get an E.
Once I get the Phantom Dancer, the kills start coming faster and faster.

So to me it seems that Vayne peeks later than many champions.
But that's my opinion.

I'll try getting some attack damage first and see if it makes a difference.

infinity edge gives ad carries the damage you can expect froma an ad carry. if you rushing zeals and phantom dancers and lifesteal, that is not going to increase your damage as much as an infinity edge.

While it is tempting to rack up attack speed quickly, there are two things to keep in mind.

1.) Silver Bolts deals more damage to targets that have more HP. Even if you max it first, the damage will be minimal in the mid-game because HP totals are still low. 8% of max HP every 3 hits is not impressive at all if your target only has 1100 max HP. (That's 88 true damage plus 60 base per 3 hits, but again, only if you max W first.) Since armor values are also lower in the early game, you can easily get more damage by just building AD and crit.

2.) Tumble resets your attack timer. If you fire off an auto attack and then immediately Tumble, your next shot will fire right away regardless of your attack speed. You can pull off a very fast AA+Tumble+AA+Condemn combo even with no attack speed increases at all.