do i need a cooling system resovior ?

Define your overheating. Running hotter then normal or puking coolant?

If you fill a radiator to the top its going to push coolant out of the overfill until it finds its happy level. A coolant recovery collects the overfill then lets it back in when the coolant cools off. Benefits are twofold. It keeps coolant off the street and oxygen out of the cooling system