"You be looking good" isn't considered proper grammar. The correct phrase would be "You look good", depending on the situation. "You look good" would be said in a present tense, such as, "You look good in that dress". "You are looking good" is very similar and pretty much means the same thing, though it's a lot more inclusive. You would say "You are looking good" when someone looks nice generally, but if you wanted to be specific, you would say "You look good in those shoes", or something similar.