I recommend Tae Kim’s guide as a supplement to anything because it’s free and easily accessible online and as an app.
It doesn’t cover everything, and I’ve seen people say that it only covers up to N4 (I’ve yet to finish the whole thing). What’s nice about it is by level 15, almost all kanji/Vocab used in the guide I have already learned though WK. It’s nice because then I don’t have to relook up words and just focus on the grammar.
Tae Kim also covers slang and important short cuts natives take along with “reality checks”, so that way you can understand differences between traditional textbooks and spoken language. Which is mainly why I use the guide.
Tae Kim focuses on teaching plain/casual form first, which I think is important for being able to understand grammar which uses plain/casual form. I also use HelloTalk, and in my experience I’ve had more people talk to me in casual/plain than polite (Genki is the textbook I use for college, and I recommend it! It teaches plain form first), but I also don’t understand the nuances yet and maybe I’m being rude…
It’s worth noting Tae Kim also has lesson excercises, but only up the past negative conjugations.
But, I only recommend it as a supplement because I think that Tae Kim can be a bit confusing and not explain things well enough. I can’t think of a good example, but I remember using Tae Kim’s guide starting out with Japanese and feeling confused and discouraged at times until I opened the door to other resources that helped me understand.
A basic guide to Japanese Grammar is good and can be gotten on Amazon, though it is a bit pricey. It’s pretty thorough and usually clears up any confusion I have.
Barons Japanese Grammar is cheap, but really should only be used as a supplement as it doesn’t really cover things in depth. I use it as a way to brush the surface of things I’ll be learning in the future.
Japanese Shadowing/日本語話そう I think is an awesome resource that has helped me with listening and speaking. A video of the audio is up on YouTube, but lacks all of the translations and additional material. The whole book comes with introduction to what the shadowing method is and a CD. My description is pretty succinct, but check it out on YouTube and maybe look into getting a copy on Amazon.
People on here have said good things about LingoDeer which is an app on the apple store, but I’m not sure about android. I don’t really use it, but from what I’ve done it’s a nice app. ️
I figure I should also mention Genki! My experience with Genki has been as a text book for my college Japanese class. The book is designed to be used in a class based on the activities and some of the workbook pages (separate from the text book). However, it teaches about culture and expressions that have taught me stuff I haven’t heard before. I think it’s worth it if you have the money and don’t mind text book learning.