There's nothing silly about the question: it's very
practical.
The diamond industry would like you to believe that a fair range
is two month's salary. Calculating that range for your hourly rate
indicates that you could spend about US$4,000. (That's gross salary
math.)
More practically, buy an engagement ring that you can afford to
buy that is of the highest quality. Purchase it from the most
reputable seller you can find.