Yes, Alclad II will show up very well over Tamiya Primer. Just make sure you sand over the primer with fine grits of sandpaper to remove and flaws and make it nice and smooth.
You only need the gloss black undercoat for the "High Shine" colors like Chrome, Polished Aluminum, Airframe Aluminum, Stainless Steel and Brass. And even then it doesn't have to be gloss black. It can be other colors to give various tones. But gloss black makes it the shiniest.