Here is a simple, short server.cfg. It doesn't set that many options but feel free to add more.
seta sv_hostname "your_server_name"
seta g_motd "your_loading_message"
seta g_enterMotd "your_enter_game_message"
seta g_motdDispTime "5" //Time to show enter message, in seconds
sv_cheats "" //if 1, then cheats will be enabled, you should instead use devmap though
g_gravity "" //default 800, changes gravity
sv_pure "0" //Set this to 0 if you want to be able to use models and skins not on the server
map mp/ffa3 //the map that the server will start