So I have loved Cait since the day she came out and I was testing this build and just started owning with it. It practically took no effort at all! Since this is the case I thought I would share this lovely IP farming build for stomping total face :D It's basically a build that uses Cait's extreme range to maximize what are the most powerful items in the game IMHO

((Mark of Desolation)) - I use these because it's a build built around ArmPen :P

((Seal of Clarity))
((Seal of Replenishment)) - Because Cait's mana regen SUCKS and being able to spam your abilities gives you a HUGE lane presence. I find a mix of the 2 runes gives you a nice balance of mana early and late game. Since you have a large enough range, you should rarely be in range of any of your opponents attacks. This means you really won't need dodge or HP runes.

((Glyph of Celerity)) - I just like being able to use my R more often, so it's a nifty choice. Other good options are Mag Resist or more mana regen. These really don't matter as much, sp I'd buy these last.

((Quintessence of Desolation)) - More ArmPen!!! :D YAYYY!!! Flat HP or movespees are also good choices.

Should be self explanatory enough. I ignore the spell pen due to the fact that neither of Cait's sources of magic damage deal enough damage to warrant it, but masteries really aren't THAT big of a deal.

My item sequence...

So this build is assuming that there is at least one person on the other team who is going to try to build armor, if this is not the case... this build actually shreds just as hard, if not harder. Rushing so much ArmorPen and damage early on gives you a HUGE boost out of the gate. But now I will go through my choices step by step :D

1. ((Vampiric Sceptre)) - with this much lifesteal and your range, you really won't need the extra health from ((Doran's Blade)), but if you're not quite comfortable with Cait yet, it's still a good choice for a starting item.

2. ((Berserker's Greaves)) - Obvious choice, but go with ((Mercury's Treads)) if they're cc heavy or the dodge boots if you're facing a team of all physical damage.

3. ((The Black Cleaver)) - Start with a ((B. F. Sword)) because the extra attack speed won't do much if you don't have the damage to back it up. This thing is brutal, especially early game. After 3 hits, there goes 45 armor, that's 70 armor with your runes. If you get this early enough, you'll be doing true damage to not only the enemy carry in mid, but any tank who even thinks thier ((Heart of Gold)) is even going to make a difference.

4. ((Manamune)) - Start with the ((Tear of the Goddess)). After ((The Black Cleaver)), you should be good on attack speed and armor penetration, so next is making sure you always have enough mana for spamming Q and always having enough for your R. Not only does it fix your mana problems, but also gives a substantial boost of damage. It has a base of 20 damage and usually by the time I'm done I have about 1200 mana, which gives me a total of 44 damage.

5. ((Stark's Fervor)) - More attack speed and life steal for you and your teammates, plus an aura that reduces all enemies armor by 20. You may be thinking that the extra armor reduction might be a bit overkill. I would disagree, since this and ((The Black Cleaver)) both "reduce" armor, which can be a huge help to your team's fellow physical damage dealers.

6. ((The Bloodthirster)) - I've technically never made this far in a game, I've always won by now, but if I was to continue building, this would be it.

7. ((Banshee's Veil)) - Get at any point if you're having trouble with a caster or if you keep getting stunned during your ultimate.

I normally get the net at lvl 2, but you can get the trap if they have a jungler or you are worried about ganks.

other than that your sequence is R>Q>E>W, but always have at least one rank of W by lvl 4.

((Ghost)) - Good for escapes and getting in and out of range for attacks quickly

((Ignite)) - Your opponent will usually have just that little bit left that ignite really comes in handy for. That and I also like it because of what it does to healing and regen

Other choices:

((Flash)) - Another good escape tool or for getting that little bit of range you needed for your ultimate

((Heal)) - If you're new to Cait and don't quite feel comfortable with her yet

((Clairvoyance)) - Good for preventing ganks and getting an opponent with your ultimate when they run into the fog

((Teleport)) - if youre lazy like me :D

((Exhaust)) - Always nice