Let me chime in on this one:
The "two months salary" is the DeBeers Diamond Co.'s way of getting guys to spend more than what has been the average in the past. So, your guy shouldn't fall for this marketing ploy. Your guy should decide how much he can reasonably afford for the wedding set (engagement ring, her wedding band, his wedding band), and stick within that budget. God willing, the two of you will prosper and he will be able to lavish somewhat more expensive pieces of jewelry on you in the future e.g. aniversaries, mother's ring with the birth stones of all your children, ect.
A lady never accepts a gift of jewelry from a man she isn't related to. The exception is the engagement ring. A man gives a woman an engagement ring with a precious stone within his means as a sign that he is serious and not just trying to bed her by a making a promise of marriage. If a guy is spending 500.00, 1000.00 or 2000.00 or 5000.00, or whatever is withing his means, he's showing her that he is serious, and she has the proof to show her family and friends when she tells them he proposed marriage.
Prince Charles gave Princess Diana a blue saphire as an engagement ring. Of course, a few hints to the guy are helpful, like complementing married women on their rings when he's around so he gets and idea of what you like.
I think the proposal should be a surprise (but not unexpected). So, he should buy a ring he's determined that you will like and is within his means, and get down on one knee and ask you to marry him, holding the ring out to you. It could be in private, but also in public (the scoreboard at Yankee Stadium is not romantic, guys). If you say yes, then the two of you can take the ring to the jewelry shop where he bought it and have it sized to fit your finger (after you've shown it to everybody and their neighbor, of course).
Now, he wants you to be happy. So he should be very, very willing to exchange the wedding set for something more to your liking BUT IN THE SAME PRICE.
Traditionally, the man buys the set, but some women these days want to buy the man's wedding band, and no, it doesn't have to match hers.
And as far as other gifts of jewelry for women:
Parents and brothers give daughters/sisters a gold chain with a precious stone pendant or a watch for highschool granduatation. The parents give a pearl necklace for college graduation, and brothers give a diamond tennis bracelet or other bracelet or formal watch to wear to work for college graduation.
Of course, a new car is always nice too.