More than 50 years ago the saying was that a fiance-to-be should spend two months’ salary on the engagement ring. Young men who did so were able to get a lovely diamond ring within their budget. That was a long time ago.
Many things have changed today, and this slogan is not adhered to the way it was back then. If budget is important, as a jeweler, I would recommend a diamond of at least 1 carat for the center stone, with a GIA grading report. In my opinion the best bang for the buck is G color, VS 2 clarity, and if possible, an excellent cut. If you can’t afford this, save up and get as close to it as possible. If you can afford more, get a larger stone with these same characteristics. A diamond is forever, and the commitment is supposed to be forever as well. The stone I’ve described above will be beautiful and will also hold its value.