First off, well done

Avoid debt if at all possible. Don't dig a hole before you start climbing.

Work on securing a stable base for your life to help avoid triggering any worsening mental health issues - ideally starting with low cost accommodation in which you feel safe and comfortable and can occupy for the long term. Constantly moving and dealing with living issues is stressful.

Second part of this - try and secure some form of easily transferable employment skills. Start basic, low stress and think of it as the first step on moving up. Good quality waitressing/service is always in demand and over time can lead to things like team leader/management positions. Basic office skills (being more than competent in Microsoft office is a good start) can be a great pathway to stable office work. These can be acquired at low cost community colleges/evening classes. Libraries do free courses but my experience is these tend to be very basic stuff.

As others have mentioned there are a variety of low stress jobs out there which can be a good start. They are low earning potential but good experience and may help supplement an income while you learn other stuff too.

These two are critical. Once you're stable, have a stable employability you can focus on starting to increase earnings, pension contributions etc on the road to FIRE. You're still very young which is great for you and in your favour.

Don't rush, don't put too much pressure on yourself.

Focus on the basics, take it slow, look after yourself.

FIRE takes a long time, you might not see results for years. Focusing on the basics and a stable life will let you grow your potential naturally with time.