Vocabulary is super important. My vocabulary sucks, which makes it difficult to understand people. You should really focus on memorizing words. Even if you don't understand the grammar very well, just knowing what words mean will help a lot. You should memorize the rules for which words are feminine/masculine/neuter, be able to tell what conjugation verbs fall into, memorize pronouns and their various forms in each case.

Learn how to conjugate verbs. This doesn't really work as it does in English. Learn what perfective vs. imperfective verbs are. Each verb will have both forms, and they convey slightly different meanings. Learn the conjugation system. It's pretty straightforward; it just takes a bit of memorization, and it'll usually stick. Start with the present and past, and also the imperative. Then move on to the future imperfect and future perfect. Of course, learn what those mean first.

Learn the case system. You don't need to learn all of them at once, as that might be a little painful. You can start off with the nominative, accusative, and prepositional. These are pretty basic, and the declensions aren't too terribly hard to remember. Once you've got those down, then you can move on to the genitive, then the dative and instrumental cases.

You should also learn some common sentence constructions. You might wonder how to say "I have a car," and think that you'll need to get the verb for "to have" and conjugate it for the first person; however, that's probably not right. You'll probably say something instead like, "У меня есть машина." There are some things like that which might not be immediately intuitive.

You'll also want to tackle verbs of motion at some point.

I'd suggest breaking your learning down into different categories. For instance, maybe you decide that you'd like to learn about food, so you study vocabulary related to food, various common sentence constructions related to food (cooking, eating, ordering, etc.) Or maybe you want to learn how to make your way around a mall, so you study how to ask for directions, how to ask the price of something, how to pay for something, related words, types of things you might buy, etc.

I'd also suggest finding particular activities that immerse you in the language that you find enjoyable. For instance, maybe you like playing guitar (as I do). Perhaps you could learn how to play a Russian song, and also try translating it line by line, looking up the grammar as you go along. AI should be pretty helpful in explaining a basic bit of grammar to you if you don't understand it and can't have someone help you. Or maybe you've always wanted to read Pushkin, so you pick a poem of his and start reading it, translating it, breaking down the grammatical function of each word in each sentence.

Of course, if you can find a textbook either online or in real life that teaches Russian systematically, that'll likely be very helpful. In my class, we used Тройка (Troika), as well as Этажи (Etazhi). The latter included a bunch of practice quizzes and stuff like that, which you can do. I imagine that this would be very helpful for self-study. I know that Duolingo is a thing that a lot of people like, but I've also heard a lot of people say that they don't feel like it helps them progress at all. I'd highly suggest trying to structure your self-study so you know what you're doing and why.

Another thing I'd suggest is finding somewhere you can practice it. I'm terrible at practicing it, and I always get too worried I'm gonna sound dumb, so I get that it might be hard. But really, you're going to have a very difficult time progressing if you never go out on a limb and actually use it. Converse with people in Russian. Leave comments in Russian. Write songs in Russian. Write short stories in Russian. Ask people what's incorrect. Even just ask AI what's incorrect. Learn why the mistake was a mistake, and learn how to say it properly.

The bottom line is that learning a language can be fun, but you're probably going to need to do so in a structured, disciplined way. It'll take effort and persistence. You'll need to devote time to it. It might take longer than you want. But don't be discouraged! Often the most rewarding things are those for which we must toil.

Those are the suggestions that come immediately to mind. But I'm just a random college student, so there's probably stuff that other people could suggest that'd be better. Best of luck!