In my life I have learned Latin, German, Greek, and Spanish.
Spanish is the only one I remain fluent in, because I use it on a regular basis.
However, the language I feel helped me most in life is Latin. It gave me such an understanding of base words that it is the one language I am happiest that I took. It also helped me a lot in learning Spanish. I never took a class in Spanish, and it is the last language that I learned, which is probably part of the reason it was the easiest. The words in Spanish are mostly derived from the Latin; and having learned the use of genders and verb forms in Latin, Spanish was easy.
I have been told that spoken Chinese is easy to learn, though each dialect is different. The pictograph language is harder of course because it is not phonetic; a certain pictograph is used for the same word in every Chinese dialect, so all Chinese can communicate by writing if not by speaking. They do have a phonetic alphabet too, nowadays.
It depends on what you want. But the fact that you are even considering Latin tells me that you are an academic person, and you would probably appreciate the benefits of Latin in terms of English vocabulary as well as learning other languages in the future.