I suggest you to go with Droplets. A droplet is a virtual server (VS). You can create as many droplets as you want and destroy them at anytime. You can create all sorts of servers in a droplet including a VS inside a droplet (Not recommending a nested VS unless you know how to configure it to manage your resources).
The good thing you will be charged daily as long as a droplet exists (PAYG: Pay As You Go). It means once you destroy a droplet, DigitalOcean stops charging you for that droplet.

Good luck

Hi there @yassermokhtar ,

It depends on what you need ofcourse ;) But I would say for a general cyber security course the droplet stated above should be good enough. If not, you can always destroy it and create a new one.