GMOD Server

As for gamemode i would recommend DarkRP or Sandbox.

For the host i would recommend Nitrous Networks or Kryptonnetworks as they cheap but very good with ping as it is always low.

And the forums i would recommend you use Enjin which if you use the free version you will get ads and it wont look nice overall but is still free and also there is MistForums which is also free but no ads and looks professional!