We want to get enagged?

We are ready to get enagged and moeny is tight at the moment. We want to be enagged over a year so we can save up money to help our parents out for the wedding we want and the honey moon. We are looking at a hearts on fire ring and my bf wants to get me the best and the setting alone is 1100. the actual diamond is 2500 more. i am considering telling him that it would be ok to just put a cubic zirconia in the ring for now and get a diamons when we can. Its not about the ring anyways its about us wanting to be together. is this acceptable? and my bf would buy a cheap ring for like 100 but he wants to get me this ring cause he says its what i deserve and he sold on it so there isnt any changing his mind there. i just thought this would be a good alternative to get things on track at the moment. Any advice?