Personally, depending on how much gear you have already:
T2i $450 used each
580 ex ii $350 used
35L 1.4 $1300 used or 24-70 f2.8 $1200 used
Later, I'd upgrade to 5d mk iii for low light ability.
5d mk iii $3250 refurbs on eBay
50 f1.4 $300