It is not about the material things. It is how much thought you put into the proposal and if you have consulted her thoughts on it. If she told you specially, she doesn't want an engagement ring (in those exact words), then don't buy her one. If she didn't say that, then she probably meant she doesn't want too much money spent on it then get her one that is not too expensive but something you put thought into selecting. Make sure the proposal is well thought out so it shows you are serious about her.