Assuming that you mean "special," I'd say that the first two sentences are correct, while the third lacks a comma after "see."
This is for someone special, you see = You are explaining to someone that "this" is for a special individual
This is for someone special, which you see = Again, you're explaining to someone that "this" is for a special individual, and the person you're explaining it to sees (i.e., understands) this
You see, this is for someone special = See no. 1 (Maybe there should be a "semicolon" after "see," although I doubt it because I think "You see" is an interjection.)
The second sentence is somewhat unlikely to be said/written, and it has a different meaning from the other two.