"Convenient for you" is generally the more grammatically correct and polite option. It emphasizes that you are considering the other person's needs and preferences.
"Convenient for you?" is a complete question, asking the other person if something is convenient for them.
"Convenient you?" is grammatically incorrect.
Examples:
* "Is this time convenient for you?" (Correct and polite)
* "Let me know what time is convenient for you." (Correct and polite)
* "Would it be convenient if we met on Tuesday?" (Correct and polite)
* "Is it convenient for you to meet tomorrow?" (Correct and polite)
When "You" might be acceptable:
In casual conversations, you might hear "convenient you?" or "what time convenient you?" However, this is considered grammatically incorrect and less formal.
In summary, "convenient for you" is the most accurate and polite way to express this concept.