If you have no audio gear, it's not an upgrade!
I guess it depends on the TV. Are you happy with it now? Is it an HDTV? Big enough for the room, etc.? You'll probably get more "use" out of the TV, so if it's a really old non-HD set, I'd probably upgrade that first.
But if it's a HD set, start with the audio. If you can avoid the Home-theater-in-a-box setups, or at least get one that uses a "real AV Receiver" and standard speakers (8 ohm, bare wire connections), you'll be better off in the long run. Most HTiB kits can't be upgraded by swapping out one part later - so you have to start over. Whereas buying an AVR and speakers, you can choose, years later, to add/swap each piece individually...