As i mentioned, the resources to run 50 users is not that big. An 4 core-8 threads cpu could handle that (including the db server).
I say just rent a server for 1-2 months, play with it, and if you're not satisfied with the performance, that's time for you to think about cloud.
If i were you i would just setup a baremetal native LAMP server, it's better than docker in terms of raw performance, since docker is running in a container.
If you don't have any problems running a server from europe DC, there's plenty of cheap one here : https://www.hetzner.com/sb