If your main shot is sport, then get a fast lens, as fast as you can afford.
But the Tamron that you mention might be too short for sport photography.
Eventhough the kit lens is nice, not everybody need the 18mm/28mm view.
28mm/45mm might be a bit restrictive but if it fits your shooting style then why not ?
18mm/28mm is not wide enough for wide angle shooting. might as well save for 12-24mm lens.
Another nod for the battery. I only have one and haven't found the need for second yet.
Aside from long tele shot, the built in flash is amazing. Much better than those p&s built in flash.
As for budget zoom, another nod for Sigma 70-300mm APO Super Macro II. I got this over Nikon 70-300 ED. But if you want to shoot sport, save up for the big guns like 80-200 2.8 or maybe 70-200 VR 🙂