<p>Chinese word order is quite similar to English while Japanese and Korean are quite distinct.</p>
<p>Tough part about Chinese is learning the tonal system and the vocabulary is vast. Even a native Chinese do struggle with advance Vocabulary but do not let it discourage you, this does not equate to being impossible to learn.</p>
<p>If you know Chinese, you will be able to read 30% of Japanese while written Korean have no similarity to Chinese and Japanese. </p>
<p>Japanese and korean have similar Grammatical structure. So this means that learning Japanese can help you to acquire mastery in other asian language. Anyway, overall I suggest you learn Mandarin first.</p>