All are ok and natual??
I wish I could be more help to you.
I wish I could be more helpful to you.
I wish I could help more to you.

Question

Answer

I wish I could help more to you. X ------> I wish I could help you more.
I wish I could help more.
I wish I could be more help.

Answer

Your first and second sentences are ok and natural.  The third isn't.  You could say, "I wish I could help you more."  Another way involves the word "of":  "I wish I could be of more help to you."  "to be of help (to someone)" is fairly common, and is perfectly natural.