Most of time, compound words use only the first onyomi of each kanji (as in 元気 → げんき). But pay attention to any onyomi that appear as suffixes (e.g.: 応 → オウ, -ノウ, 反応 → はんのう). That said, don't bother trying to learn *all* possible readings in one stab, especially the kunyomi, as most are exceptional. You'll be able to spot more of these exceptions with time and practice.
As for the kanji meanings, don't bother too much too, as in some compound words that meaning disappears or just makes no sense. They may help you, whoever, remember what a compound word is, or even guess what a new, never seen word is ─ same when learning onyomi, which may help you guess the pronouciation too. (YMMV)
But that's only my opinion, though. Let's see what more experienced friends have to say ;)
March 29, 2017 at 11:35pm