This behavior will make the merchant more likely to take you seriously. The diamond industry tries to convince you that a ring should cost you two months salary. If you want to go along with that, fine, but don' t spend money just for the sake of spending money. If you see the perfect ring, but its price is less that two months of your salary, then just pretend like it cost more and pocket the difference. You may think that it's intimidating to go into a fancy jewelry store and haggle over the price.
Jewelers are just car salesmen without the complimentary donuts.
Get a diamond. Get a diamond. Get a diamond. Shut up, suck it up, and get her a diamond. Many a little girl has gone to sleep at night dreaming about her first diamond ring.