I'm happy with DigitalOcean 5$ droplet, is more than enougth to run a medium size Flarum community.
I think that DigitalOcean website is clear enougth, is quite simple compared with most of providers. But maybe offer many products that you don't need and maybe is what seems confusing to the new user.
The other providers i tested was Vultr and Linode. Both are also good, i can't see that you go wrong choosing any of them.
All of them have port 25 blocked by default, so you have to request to support to open it. If you don't open it, SMTP will not work.