the sender should get a ground from it's mounting screws to the tank and the tank to the cab, and the factory setup is a ground from the battery to the cab, but it never hurts to have extra grounds .... sounds like all is as it should be, so when you turn on the key, the needle should move up, unless you have a totally empty tank .... have you tried clipping a wire on the sender terminal of the gauge and touching it to ground? if there's no action I'd guess the gauge is the problem .... the other question is whether you've checked the action of the sender and it's resistance value, you don't say but moving the float thru it's travel should give a value of 0-30 ohms [not 0-90]
Bill
