加之, 再者, 况且 — and one more thing

규칙 加之 = coupled with — adding another CAUSE to a chain already given: 天气不好，加之路远…
再者 = furthermore — opening a new POINT in an argument, at the head of a sentence: 再者，费用也太高。
况且 = besides, and what is more — a STRONGER reason clinching the case: 我不想去，况且票也卖完了。
此外 = in addition — the neutral one, simply listing more.
加之 joins inside ONE sentence; 再者 and 此外 open a new one.