Getting soil ready?

I was planning on using Foxfarm Ocean. I've heard people say you need to mix sand or pearlite into the soil.

Is ther necessary for Foxfarm? Is there soil that i wont have to mix anything into?

Any other soil recos?

Shouldl i put rocks or something at the bottom of the pots?

Anything i'm missing?

Thanks, you guys are great!

NO ROCKS. Buy a bag of perlite, mix like 1/4 to 1/3 of the bag into each pot (if they are 5 gals) Otherwise (say 3 gallon), use like 1/8 of perlite out of the bag. just guestimate