Hi all, i started wanikani 2 months ago and im enjoying it for the most part but im really struggling with the readings. I can remember the meanings well but im always getting caught out on the reading, particularly with the rendaku changes or onyomi and kunyomi changes. Ive been trolling through the forums and reddit to see if there is a trick i am missing. I read each reading mnemonic twice through when i do a lesson and i always read the mnemonic again when i get one wrong. I even stopped doing new lessons for a week to try and get my reviews down and my apprentice items down to 50 so my last level up took 25 days. My native language is English, am i missing something, any tips or tricks would be greatly appreciated.
Pics for reference and examples
Don’t worry, over time they will be about equal. Eventually you will stuggle with meanings as well. 
Jokes aside, I remember I had this issue too, but over time as more and more kanji used the same readings, I relied on SRS and eventually you will remember it. You need to remember more words to get some understanding on what sounds right and things will be easier.
writing your own mnemonics can help tickle your memory a little better
This is mainly an issue in the beginning stages, where you get a ton of japanese readings instead of jukugo words with chinese readings. Later down the line the issue will flip around and guessing a reading will be easier, but deriving a meaning quite a bit harder in my opinion.
For On-On vocabularies, or Kun- without Okurigana, it’s as simple as inferring from related vocabularies. (And that also helps remember Kanji readings.)
I would also say that the trick is listening… also with good ears.
For vocabularies with Kun in many cases, it may be possible to split to smaller vocabularies disregarding the Kanji. Sometimes Kanji was substituted, hiding the underlying etymology; but other times, false etymology or folk etymology may help.
If nothing works, maybe just mnemonics. Creating your own if WaniKani’s don’t work well, may payoff better than trying to choke in WaniKani’s mnemonics.
Not use about 用いる. Maybe 持ち + 入る.
You can at least be fairly sure it’s not よういる, because よう is the on-yomi and kanji+okurigana is going to be the kun-yomi.
Apparently etymologically 用いる derives from 持ち (mochi, the 連用形 (ren’yōkei, “stem or continuative form”) of verb 持つ (motsu), “to have, hold”) + 率る (iru, “to bring along”). Though since that last part is pretty obscure I’m not sure that helps much as a mnemonic.
I think I remembered this one as “it’s an odd reading that sounds like it ought to be a compound verb but isn’t”, mostly remembering it because of its strangeness; but I came to this word rather later in my learning journey than WK hands it to you.
Which いる aside, several vocabularies have the same form, i-row + iru.
Writing them in a book helps when taking the lessons, atleast for me.