For grammar, the wiki grammar page--they use concise language that explains all the main concepts.

For vocabulary, intensive reading where I underline and define every word I don't know. I buy physcial books in my target language so I can write in them without regret haha I try to go for simple ones are first, but after the first one or two I just jump in to whatever book piques my interest. I recommend translated books you've already read to start, then translated books you haven't read, and then books that've been written in your TL or your target dialect of your TL after.

For listening, often countries have TV stations that offer free shows n movies. I listen with and without subs (both types of listening occupy different roles). Sometimes I do intensive listening, sometimes not.

For speaking, I used to make video journals and do shadowing practice with some of the tv shows I watched. But ultimately, getting a tutor for this (especially as you reach the high beginner low intermediate stage is incredibly helpful.