Which one is more appropriate to use: "send you" or "send to you"?

Solution 1:

Both are semantically correct as they are. But compare

I'll send it to you.

and

I'll send it you.

The second sentence wouldn't make sense in formal writing, but is found to be understandable in northern England spoken usage. There is also the case of

I'll send you this thing

Which flow much better without the to. In this light it might be more prudent to use send to you, as it is more formal, but send you in your context would also be accepted.

EDIT: I precised my conclusion and added one example following precisions made in the comments.

Solution 2:

In addition to what others have said, You can simply find out the difference comparing two sentences: send somebody something

We sent Mom flowers for Mother's Day.

send something to somebody/something

I'll send a copy to you.