Yeah, I noticed the thread was repeated too late and I jumped on the Johnny No-Friends one by mistake
You've added another dimension to the mix: upgrading, so I thought I'd comment.
> ... and if I find myself really doing a lot of this stuff then I could upgrade
> to something a bit more quality.
While you're experimenting, it's great to go low-budget and sort out what you're really after. But there's one thing I can't stress enough in your initial buy that you need to be aware of.
If you _know_ you're going to upgrade your setup, invest in a decent studio microphone from the outset. That's your priority right there. If you're kinda not sure if you're going to expand or not, get the cheapest, rattiest microphone you can borrow/ buy. No point wasting good money for sound quality if you're at a stage where you don't need it, won't appreciate it, or you're going to run it thru so many effects filters that you may as well have yelled into a can tied to your comp with a piece of string.
Your microphone is key. Your mic is the first and last wall of quality sound from the acoustic environment. You will record vocals, acoustic instruments, samples and sound effects with it. Your mic will faithfully record breathing, fret noise, as well as your acoustic environment's background noise if your room isn't treated nicely.
So, depending on your priority of use, your microphone selection determines the range of novelty, or original sounds that go into your GB recording. If you're more interested in your electric guitar sounding hot than your vocals, skimp on the mic budget and throw it more toward something like the 410, or a MIDI controller keyboard.
The second 'budgetary' consideration will hit you completely from left-field: treating your room

Ideally, your mic will be positioned in a shock-mount, on a stand that's resting on a solid floor. If you have a bouncy wooden floor, you risk adding your foot-taps to the mix, for instance. If you have a powerful voice or wind instrument, and a boxy room, you'll eventually want to take to your room with a tape measure to work out what frequencies those damned re-inforcing standing waves are, and dampen them with foam walls or good ol' egg cartons, etc. Otherwise you'll find you can't mix some acoustic melodies properly, becasue some notes sound a lot louder (or tinnier) than others.
An alternative to insulating your room is buying an expensive Graphic Equalizer, or spending an inordinate amount of editing time adjusting the volume envelope on your tracks. The latter solution sounds the easiest, but trust me: your first pass will hack you off enough to realise you won't want to go thru that again. It slows you right down.
And all the dampening in the world isn't going to save you if your mic is positioned right by your computer

If you're happy with your computer's fans, hard-drive spins and CD whizzes in the mix, you may as well use the built-in mic :-D
The rest of the equipment is just middle-management, trucking the signal to the computer. The M-Audio 410 FireWire is a nice all-rounder solution, but that's a hella price. In my opinion, it's also a little overkill for someone starting out on a product like GB. You just want a simple chain from mic to computer, without having to switch between GB and another window for mixing and balancing. But again, this is the interface/ budget trade off everyone faces, and one solution doesn't fit all.
If you were to give me more specific ideas on what you want to use GB for (just mucking around/ learning music/ scoring videos/ music notepad/ theatrical background/ sound effects/ post-processing) I could possibly throw more ideas at you with a view to saving money while maximising efficiency.
Hope this helps,
-Oro