Assuming you are single, here is what I think could be a breakup for your expenses:
1.housing: 10K ( check with your company if they will help you with 2 months initial deposit payment)
4.Travel(to work ) + phone: 1.5K
On top of this, its up to you how much you want to spend on entertainment/going out with friends etc.
Remember, there is no TDS here and you get everything in hand. However, you need to pay taxes in 2 installments towrds end of financial year. In HK, you also need to pay upfront 75% of tax for next year.
Agreed that the offer made to you does not have the "wow" factor but if I were you, I would take it.
1.As you are single, you have more time to settle down here before you get into a relationship
2.HK experience should definitely add value to your CV.
3.Get started first. Nobody is asking you to stick to the same company at same salary for the rest of your life.
4. At 25, its a good time to exlpore a new country, new culture, meet ppl from different backgrounds and learn new things.
5.My personal opinion: I find HK better, cheaper and a lot more safer than other countries that I have worked in.
Just my 2 cents. Hope that helps.
Disclaimer: The expense numbers I have given above are just what I think I can manage with. The idea of "decent living" is relative.