What to focus on to get my first job in tech at 25 years old, non-CS degree

First, I recommend the overall job searching course: Ace Your Tech Interview And Get A Job As A Software Engineer

Second (and I sincerely wish this wasn't the case), the market is absolutely brutal right now for junior engineers, especially self-taught ones like yourself. Because of this, I recommend going all-in on your friend's startup: Can you work for them for free? If they can't do that due to labor laws, then just take minimum wage. Your goal right now is just to get experience.

If you still need to interview for them, then you should spend most of your time building high-quality webapps with React, Next.js, and TypeScript. These are all industry standard technologies, and even if your friend's startup doesn't work out, the experience will still be valuable.

Your biggest problem will almost certainly be getting any interviews to begin with, not solving LeetCode problems (this becomes a problem after you start getting interviews). It's rough as I'm sure the bar will be high. If someone had your background in the US, the minimum they would need just to get calls back is building a side project with 10k+ users or 100+ major open-source contributions or something. When a candidate doesn't have work experience, the recruiter/hiring manager will fall back on a Computer Science degree (ideally from a top school). But if a candidate doesn't even have that, you simply need to stun them with something impressive.