Well, as you can see, there are a lot of possibilities!
I think my main suggestion would be to try out lots of things (particularly if they’re free) and just stick with what works well for you. I’m not sure what you’ve been studying from so far, but…
Lots of people like using the Genki textbooks, but they are designed for classes rather than self-study so I definitely know a number of people on these forums don’t get on too well with them.
Tae Kim’s Guide is a free grammar resource which is structured pretty nicely. I think the main complaint against it is that it is a bit ‘shallow’ - but you can supplement your grammar knowledge by going through other resources at a later date.
BunPro was created by some WK users, and seems to be very popular (I haven’t tried it myself). It uses an SRS like WK, and points you in the direction of grammar explanations. Be aware that it is still in development though.
But really, you should just try to find a textbook (physical/online) that works for you. There have been a variety of threads in these forums where people have discussed the differences and preferences for the different textbooks available, so I would just have a search through the forums
I hope you find something that works for you! Welcome to WaniKani