I have used Digital Ocean for the last four years and I can say that it is one of the best cloud services I have tried, not just because of the cheap costs, but also because it is super easy and fast to configure, and the community has a lot of updated documentation to fix most of the common issues related to the server configuration.
At this point, you will need to invest some money to get this service. I will show you the cheapest way to do this, and if in the future you want to increase the power of your Droplets, you will be able to increase the capacity without redoing the configuration. The lowest price for the very basic Droplet is $5.00 per month ($0.007 per hour).
The latest LTS version of Ubuntu is 18.04; you will need to know some basic Linux commands to be able to configure your Droplet. If you're a beginner using Linux...
