As it’s a demonstration of love and compromise and so a very emotional purchase, there isn’t a defined quantity for the purchase of a diamond. The common practice in Europe is to invest a quantity equivalent to the salary of two months.
There are diamonds of all the prices so it’s not difficult to find one that fits into your budget! It depends on the person to decide how much can spend and also how wants to spend.
The right diamond
You should choose the right diamond for the ring, you will need to value the diamond 4C’s and then decide the shape!