@tunda I'm currently running this on an AMD Sempron singlecore processor with 1,5GHz and 1GiB RAM. That works quite well since I'm the only user. Peertube consumes ~75-100MiB of RAM idling.
If you plan to have more users, I'd recommend at least 4GiB and a faster processor with more cores. But I've not tested it, I'm making merely an educated guess.
Keep in mind that every uploaded video will be transcoded to different sizes, which will consume a lot of CPU cycles.