Triggers, you can use the good 'ol PT-04tm aka Cactus radio trigger which cost about $45 per set but receiver is only about $25 each. I have however moved to Elinchrom Skyports. Not as expensive as PW Transceivers or the Flex/MiniTTIL but reliable still.
As for the strobe, the cheapest would be to get good 'ol Vivtar flashguns - you get light of course with perhaps the least bells and whistles. Next would be third party flashguns but am not sure if it has sync ports like the 580EXII or SB900. The most expensive but reliable would of course to get the 580EXII since you're using Canon. With the PW Flex/MiniTTL, you can use E-TTL mode via radio trigger, the rest just trigger your flash. However, if you're not looking into flashguns, monolights which give you at least 3 times the power of any flashguns, like the Jinbei Delicacy 180W/S is something you should consider. The kit is only going for less than $500 and you get 3x 180W/S strobes. I had these but have moved to Elinchrom D-Lite4 Kit which consists of 2x 400w/s strobes.
Flashguns, according to the internet, gives a max output of about 55-60w/s. Not sure how true is that but from experience, flashguns are just no where as strong the cheap Jinbei Delicacy. That said, like many others, I've used Canon flashguns for outdoor lighting without much compromise and still doing so until I get myself a decent batt operated strobe. The use of battery pack is recommended though, flash recycling time can just dissolve momentum during shoot, "eh wait ah, my flash recycling.... ok here we go..."
If you have loads of cash, look at the most robust flashgun, Quantum Qflash system - not the Trio but QFlash -
www.qtm.com. Why loads of cash? Cuz one Turbo QFlash (About 200w/s) with Turbo battery pack will set you back about SGD2000.