I’m seconding slow and steady! I’ve had pretty good success with focusing on just a few resources at a time that I can work on daily. Right now, I’m doing WK (and Kaniwani, though that is tied to my WK progress) and am working through the textbook Minna no Nihongo. MNN is teaching me vocab alongside grammar, and I’m not doing any other flashcards or grammar exercises outside of what I’m learning in the textbook. I’m going pretty slowly through it, because I’m waiting until I’ve learned the vocab before I even start trying to read the lesson, but it’s nice to see steady progress with a workload that isn’t overwhelming (I do use Anki to learn the textbook vocab, but most days, it takes me less than five minutes to run through my Anki deck).
My big recommendation would be to establish a daily routine with WK that doesn’t interfere with the rest of your life (I recommend doing a set amount of lessons every day so that the workload stays roughly the same on a daily basis), then after you’ve fallen into a good rhythm with WK, pick one other resource to supply grammar and try to make that one a daily habit as well. I prefer using a textbook for this because it teaches both vocab and grammar bundled together (as well as giving me some listening practice, reading practice, writing practice, etc.). It can be difficult to motivate yourself to work through a textbook, but if you’re meeting with an instructor, that person could help keep you accountable. I think the danger comes from having to build your own study schedule and giving yourself way too much to work on (I don’t know how some people can manage WK, a grammar SRS, and a third SRS for additional vocab, all at the same time!).
If you’re feeling overwhelmed by the amount of options available, maybe going more traditional and trying a textbook would be a good idea? Textbooks structure your learning for you so you don’t have to worry about finding different resources for grammar, vocab, etc. You can eventually supplement with native material, but a textbook can give you a solid foundation to work with (and will teach you about multiple aspects of the language all at once). Tofugu has an article with a bunch of textbook recommendations. I’d look at this and see if anything on there speaks to you.
Some people on this forum hate textbooks and recommend immersing yourself in native materials as soon as possible as a primary way of learning, but I’ve found that immersion is way more effective for me if I combine it with more structured learning, so I’m not planning on trying to read manga or graded readers or anything until after I’ve at least completed the first book of MNN (which’ll put me about at N5 level, grammar wise). The truth is, there’s not really one perfect way of learning that works for everyone. Some people have used textbooks and learned Japanese really effectively. Other people had a terrible time with textbooks and found success through other methods. I think focusing too much on what is the most “efficient” or “effective” method often leaves us paralyzed by indecision. The most effective method is whatever you are able to keep up with!
What are some of the things you’ve tried in the past? If you tried immersion and found it too frustrating, then maybe you’d have better luck working through a textbook. If you tried a textbook and couldn’t motivate yourself to study, then maybe you’d have better luck trying to read native materials and looking up grammar as you go. If you tried balancing a bunch of SRS all at the same time and got overwhelmed, then maybe you’d be better off sticking with just WK (possibly going at a slower pace), and learning vocab and/or grammar without using flash cards.
It’s okay to focus on just a few areas of the language at a time, like learning kanji and getting good at reading, or focusing on speaking and communicating with other people. I think as long as you’re moving toward actually using the language in some way, whether that’s engaging with native materials or communicating with other people in it, you’re going to progress towards fluency. You can always work on certain aspects (like learning to write kanji by hand, for example) after you’ve gained a comfortable level of understanding in others. I think it’s a good idea to learn multiple aspects of the language at the same time so that you can work toward actually using the language in some form (like kanji and vocab and grammar, for example, because that will allow you to read), but I don’t think you should feel obligated to work on absolutely everything at once!
