The reddit post you link to is rather old. Why don't you try http://swarm-gateways.net now? We have a brand new cluster backing the gateway.
It is true that it has been down a lot in the past, but that is because swarm is under heavy development. It will only get more stable with time.
To run your own swarm node, simply follow the swarm guide: https://swarm-guide.readthedocs.io/en/latest/
This will give your own private window into the swarm at localhost:8500
If you want to run a public gateway, just run an nginx reverse proxy for localhost:8500 :)
server {
server_name my-swarm-gateways.net ;
listen 80 ;
location / {
proxy_pass http://localhost:8500;
}
}