the first and most important thing is to stick with it. do your reviews regularly, make it a habit. it will seem slow for the first 10 levels or so, but then you will get overwhelmed soon. use this time to watch yourself and find out more about yourself. don’t assume you know how to study japanese before you actually studied japanese. I’ve tried lots of things before wanikani and I was not sure about it, but after a few levels I knew it was worth the money. Maybe it’s different for you, but as I said, you won’t know until you try. As for me personally, I haven’t done anything in particular besides WK (for reading), but I really like textbooks and just “getting a feel” for the language by reading as much as I can (in the wild). I revived some of my burned items twice (a couple of hundreds each time), because quantity trumps quality. My credo is not to trust myself: I will cheat if I get the chance, so I try to make it as hard as possible for myself.
Don’t fear mistakes, it’s more important to do a lot of things that may be wrong than to do only a few things perfectly. I also really don’t care about considerations on “efficiency” when it comes to learning (a language).
and even if you don’t like the mnemonics, they will help you. best not to ignore them. The best mnemonics are those that will make you go WTF and “why should I learn this mnemonic? this is stupid” - those are the ones you won’t forget.