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
7d, 5d mk iii, 1d4, 1dx, 35mm f1.4L, 70-200mm IS ii USM, 300mm f4 IS USM, 600mm f4l is USM, 400mm f2.8l is usm, 14mm tamron f2.8, 17-40mm f4L, 24-70 f2.8L USM, 85f1.2L USM, 100mm f2.8 macro