Quick question: which is more suitable, staining or waxing? I think this floor, for example (from that gapseal website) looks wicked. Has it been waxed?
Staining doesn't necessarily put any kind of protective coat onto the wood (it might, but you'd need to check). Waxing, on the other hand, impregnates the wood with a layer of the wax which will prevent spilled liquids soaking in and perhaps staining the boards unattractively. It also provides a coat which will stop grime and dirt sticking to the boards.
And you can get coloured waxes, so you're effectively staining as well. Most of the shelves I've put up at home have been treated with coloured Briwax.
Either way, you need to seal the floor, first, using a proprietary sealant. Have a look here -
http://www.diydoctor.org.uk/projects/timber.htm - for a bit more detail.
Me, I'd probably wax. But if you want a really hard-wearing finish, you may be tempted to go for the varnish option.
One tip - if you wax, you'll probably never get it off again without a lot of grief if you change your mind: you'll also have a problem getting any other finish to take once you've waxed a surface. Varnish, on the other hand, is more of a surface coating, and can be taken off relatively easily.
If you're on a budget, you can do what my dad tended to do, and just oil. You can do this with linseed oil - mix it with some white spirit for the first few coats, then switch to neat oil, and just keep rubbing it in until the floor won't take any more. Ideally, you do this over a period of time. There's specialist oils, too - "Danish" and "Teak" oils. They mention oiling on that web page I gave the link to above.