You can buy a Windows or Linux server it doesn’t matter. They’ll give you SSH access. They offer a free control panel for it so if you do order make sure you mention you would like to have the free control panel added. It’s makes things easier if you’re not use to SSH.
1 Core is plenty, I have the 4 core because I run other things off it. If you’re unhappy with it they offer I think a three day money back guarantee and you’re also able to upgrade if you wish. But the 1 core should do the trick.