I think the OP has got his priorities/thought process around the wrong way. Key questions are what is his intended career path (e.g. accounting, law, finance, etc), and why does he want to work in HK. How important is it to work in HK (i.e. is it a nice to have, or something which you must have at some point, or something which you must have as your first grad job). I use 'he' loosely as it may be a she.
In pretty much every Commerce field, there is potential to work in HK and in some cases it's more desirable than others... but realistically if you are wanting a company/firm to sponsor and transfer you to HK, you need to show that you are both of a sufficiently high quality to make it worthwhile (either the company needs to get a benefit from you coming back and increased skills/experience/loyalty, or you need to be good enough to transfer over so they don't look like idiots for sending you), and also you need to be able to fit in with the locals for whatever reason. Knowing cantonese is obviously a big help over there, but it also depends what nationality/appearance you have- if you look Asian, you'll be socially expected to know cantonese.