Engagement ring

How much should one spend on an engagement ring ?
I'm a fairly low paid guy, maybe €40,000 a year. I have planned to fly to Dubai to buy one, as the prices over there mean the saving should more than cover the cost of flights and accomadation. I should add, that i ain't travelling so far to save money, just to get a better ring for my angel for my bucks.
So, if you were buying in your country, what would you spend/did you spend, and is there a conventional rule for these things ?
I'm a fairly low paid guy, maybe €40,000 a year. I have planned to fly to Dubai to buy one, as the prices over there mean the saving should more than cover the cost of flights and accomadation. I should add, that i ain't travelling so far to save money, just to get a better ring for my angel for my bucks.
So, if you were buying in your country, what would you spend/did you spend, and is there a conventional rule for these things ?