Thanks Etiennne.
I use a Canon Speedlite 430 EX II however, I also have a Yongnuo YN-560 III flash which only cost £50 (not sure what it would be in your local currency but they're very cheap in comparison to Canon and still very good).
It doesn't have ETTL so you would need to use full manual flash but either way, combine that with some decent diffusion and you can light your subjects nicely.