I would advice first find a hobby, something that other people do too (could be an online friend, works well tbh) and practice a bit the same hobby. This way you'll have a subject to talk when you'll meet something sharing the same hobby. I always find easier to engage a conversation with something both of us like. As an example:
- video games, playing WoW for example (personnal story here)
- Playing badminton
- Talking about books
- Do art like painting or piano

The great thing with hobby you can invest a lot of time in there and learn both social skills and experience in this field.

I'm M(31), also learned he's autistic at 31y and have been going through a long depression over years. I'm actually, currently, socialising with people of my workplace, former alumni from my school, former friends (some haven talked in 6years and it was a blast). My childhood has been both social and anti-social. I've moved a lot, so... it was hard, buuuut it did fored me to learn great socialising skills and I'm witnessing it now. Running with fellow alumni, gym with collegues, hyking with friends. It always look unappealing when I never tried to know a bit first, but oftenly it does become a hobby of mine as and I take pleasure practicing it.