I think the first step might be to take a look at the tutorials, searching for the relevant, then settle on the distribution you want to use or that seems to have the most documentation support for what you want to do. Once you’ve decided on a distro then I’d systematically set things up.
Do the initial server setup in the distro you decided on. I personally like CentOS but a lot of people like Ubuntu but I’m not tied to the distro I like the most, I’d go with what seems to support what I’m trying to accomplish the best, including tutorials. I’d say Ubuntu and CentOS seem relatively friendly to those without tons of experience.
Once you’ve done the initial server setup, look for recommended steps, especially security related to complete.
Then in case you want to backtrack without having to start completely over, this might be a good time to make a snapshot( a type of backup).
Then I’d start going through the tutorials covering what you want to do, asking questions here in this forum and also to the support department at DO.
I don’t have the time now to check if everything you want to do is documented in the tutorials and other DO resources so I’d be interested to hear what you find. Since these are Linux servers you’re also not limited to DO’s resources, I sometimes search the web for answers to questions or to help solve problems.
Since you mentioned you’re relatively new to this, I’ll mention that I think it’s important to be mindful of security as you proceed with this. For example, make sure to take the time to setup a firewall. I’m mentioning it as I could see how it might be tempting for people to skip steps to deploy faster, a tradeoff that might be harmful and time-consuming later.
This tutorial explains the first steps you need to take after creating your CentOS 7 server, including how to login with root, change the root password, create a new user, give the new user root privileges, change the SSH port, and how to disable root login in.