Eventually you'll find that the better approach is to learn compounds rather than single character/single readings. However, you need a base from which to start. There isn't a single source I know of, but what I did was use a made for Japanese schoolchildren kanji dictionary of the first 1006 elementary school kanji. Mine was a Doraemon one which was a bit embarrassing to carry around, but there are a few different ones. For each character there will also be compounds using that character. Looking at the readings for the compounds you can see which on reading is the most common, with reasonable confidence. Alternatively, use a site like http://jisho.org/kanji/ and input the kanji in question. Then chose from the "words beginning with" and "words ending with" links and scan which reading appears most. (Also, on the results page there's a checkbox to restrict the results to "common words only".) This should also help figuring out which kun reading is most common.

I find the first onyomi listed in the kanji dictionary to be usually the most common reading. Easier words have the most variation when it comes to onyomi readings. As words becomes harder and harder there is often only one onyomi reading. I don't know a good way to find most often used kunyumi. I don't think there is any rules.

It would be some of your help. https://www.coscom.co.jp/japanesekanji/index-j.html English https://www.coscom.co.jp/japanesekanji/index.html

It's better to watch Japanese anime and series or live with Japanese people to learn what they use or not.after watching many hours of anime you will be able to easily detect each word and useful kanjis.