By chance, have you seen these topics?:
- The “What Do I Do Now?” Thread - Free Resource List
- The Ultimate Additional Japanese Resources List!
As for grammar, if you’re not ready to buy Genki, I suggest looking into the basic grammar section of Tae Kim to get your feet wet. Personally, I went through that guide before I started Genki I and I feel it put me in a really good position.
Imabi is an excellent resource for learning and it’s extremely thorough.
jtest4you offers multiple choice quizzes and grammar explanations divided by JLPT levels.
If you like youtube lessons, Japanese Ammo with Misa is a must.
You could also look into free apps to help you along the way. Obenkyo is great. Once you learn verb conjugation, Japanese Conjugation City is awesome for practicing. And I think that’s the most important point and why a lot of people do so well with the Genki books, as you really do get the opportunity for so much practice. So if you’re going to use alternatives to a textbook/workbook combo, make sure you’re making up your own sentences to use what you’re learning.
Good luck on your Japanese-learning journey! 