If you want donations, do not reward donators with things that influence gameplay. Give them cosmetic things. For example, in my TTT & Zombie Survival servers donators receive titles (words above their head). I also reward them with reserved slots. However don't make it kick people out. Make extra invisible slots only usable by donators for when the server is full. For example, my TTT server displays as having 24 slots but it really has 28 in case it gets full and a donator wants to join.
Also, I recommend
NFOservers as a host.
Oh and also, never sell administrator priviledges. Ever.