I don’t think you’ll be able to do it with that little disk space. See Set up Discourse on a server with existing Apache sites. There is a similar topic about nginx but I can’t find it in the link search box.
I recommend that you first install on another vm to see how things work before attempting an advanced installation.
It’s possible to use some of cloudflare caching, but it’s speed up features can break discourse. There are lots of topics about problems people have caused with cloudflare.