Grocery panniers can be had for as little as $15 on sale. For several years I used the
Nashbar Townie Basket grocery panniers. They're usually around $20 each, about $15 on sale a couple times a year.
Last year I upgraded to a pair of
Arkel Shoppers. I needed more capacity and a bag that could more easily be carried into the store then mounted on the bike while full. The Townies are difficult to mount when loaded, whereas the Shoppers mount easily, one-handed.
Here are pics comparing the two. Nashbar Townie on the left, Arkel Shopper on the right.
The Shopper is half-again as big as the Townie, but the Townie has no cover at all. Still, only twice in four years did anything bounce out. But I could never really fill them full. In contrast, the Shopper has a cinch cover that also serves as an extension, permitting even greater capacity.
Shopping for one and with no pets, I needed to shop twice a week with the Townies, but only once every week to ten days with the Shoppers.
As for racks, I recommend dual-siderail models like the
Topeak Super Tourist DX and the
Tubus Cosmo, which is what's shown on my bike. Mounting the panniers on the lower siderail lowers center-of-gravity for better handling when loaded, and leaves the rack top available for other things--for instance, bungeeing big packs of TP to it, or a using a commuting trunk bag.
EDIT: Finally, I don't know dick about track bikes, but I know roadies. Regular racing geometry roadies don't like heavy loads on the back. Or at least mine doesn't. It's all squirrley and skittish. The front/rear weight distribution is off and I have to focus to keep the front wheel on the ground when climbing. I have to slow to a walk for cornering.
My regular commuter (2006 Trek Portland, shown above) is based on cyclocross bikes, but has slightly longer chainstays in the rear, although not quite as long as touring bikes. On the Portland, I can forget the load is even there. In fact, the bike seems to like carrying a load. Ride is improved and handling is not affected at all. It's only when at a stop and I have to hold up more bike that I'm aware of the load.