I carry three cameras with me to all shoots. Up until recently I have had a back-up of every piece of equipment, but I've culled that down some by using lenses with overlapping capability and selling off some of the dupes.

You can do a lot with a simple speedlight, inexpensive light stand and an umbrella, while you're waiting on getting a set of "real" strobes.

I don't know Canon well enough to judge whether you have a "good enough" body to start with, but in general, lenses are always a better investment than bodies. That said, if you only have one, I would certainly look at getting a back up.