How powerful should my hardware be?
I think 512mb ram is probably a bit too low. There is a risk for the pc to crash at some point. I think 1 GB+ should be fine.
Which ports do I need opened to operate a lemmy instance for my personal use (i’m only going to be connecting from home)?
To avoid opening ports you can use Cloudflare tunnel as you mentioned.
Only other option is probably renting a cheap vps. Here is a cheap vps options for 2.5$
Anyone is welcome to join my instance at endlesstalk.org. Its running on a pretty beefy server, so it can take a decent amount of users.
There are multiple frontends like lemmy.world and I have setup a seeder(lemmony), so the all feed should be pretty filled.