Be nice. Or else.
Neat gets my vote.
I agree with a lot of what Erik has said. The only thing I would add is to learn SASS. Foundation is built using SASS, there is a version of Bootstrap that uses SASS also as far as I know. Lastly you could go the route of using little composable frameworks like Neat, Bourbon, and Compass. I personally like using Normalize, with Neat and Bourbon. I hope this helps.