From what you've described here, I think you are a Canon EOS user. Correct me if I'm wrong. What Canon body are you using?
You might not want to compromise on lighting if you wish to shoot events; not all events are held in the presence of good proper lighting conditions. The advice is to go for the highest end, but that might put a strain on your low budget.
These are some recommendations of my own opinion. They are at least 2nd (or lower) in line to the top end in each range...
1) Canon Speedlite 550EX or the older 540EZ
2) Metz mecablitz 54 MZ3 with SCA 3102/M2 or 311 adapter
3) Metz mecablitz 44 AF-4C
4) Metz mecablitz 40 MZ3i or MZ2 with SCA 3102/M2 or 311 adapter
5) Metz mecablitz 36 AF-3C
6) Metz mecablitz 32 MZ3 with SCA 3102/M2 or 311 adapter
Some models may not be available in Singapore.
In fact, I'm waiting for a shipment from an ebay seller in Germany of his Metz 32 MZ3 flash unit.
Even though the 40 MZ3i is still available in 2nd hand shops in Singapore, I didn't like its bulkiness which is on all sides. Very difficult to fit it in your camera bag if you have many stuff to carry.
Some metz links you might want to check out on your own...
http://www.metz.de/en/photo_electronics/flashlights_digital.140.html
http://www.metz.de/data/sca_archiv_eng/archiv_neue_mbs_head.html