Don't use CloudFlare or any CDN/AntiDDOS services because they decrypt all traffic that goes to and from your server[2]^. You don't know what they do with it.
DNS queries sent by the server should be encrypted[3] so that the ISP/data center cannot see them.
If you want a VPS: try getting KVM instead of LXC one. It's so easy to automate processes scanning on the fly[4]
To really be censorship resistant you have to follow the example of the pirate streaming services. Have servers in multiple places. Multiple domain names. Be resilient to any instance going down.
Any capability the server has to violate user privacy a government has. So ensure you have as few capabilities as possible to violate privacy. If your users are very vulnerable make sure that you don't have the data to expose them ever.
You can consider hosting in a "safe country" That's just the beginning. You could make your service available on tor via hidden service address. That way even if users don't have good operational security themselves you try to protect them from leaking their activity to whoever their vulnerable to
Switzerland, Iceland, Finland, Spain, Egypt,Sweden, and some 3rd world countries that don't really give a shit (though they might give a shit if your country makes them give a shit)