I'd like to test it before I go buy a Raspi or host a server.
Sort of, yeah --- I assume you should be able to do this with a VM. Virtualbox is free -- as is Debian/Ubuntu/Whatever. From there you can install pihole and should be able to get going. Set up your guest with bridged routing, and us ifconfig to make sure you're actually getting an IP from your router.
A lot of providers really do frown on running an open DNS resolver on their networks and will shut them down flat very fast. (Or just firewall the traffic off.) The best way would be to try a VPS solution, but we do not track or publish public DNS servers since they are a security issue to have running free to use for any client.