Not exactly crystal clear!!

by Dan Coventry
(Canada)

I have a number of good friends whom I entertain in my home at Christmas formal dinner. A couple of years ago these friends got together financially and purchased a collective gift to present to me as the host. The idea caught on and it has now become an anual tradition. The first time they pooled their resources the gift I received was a set of four crystal tumblers for my bar, and they have continued to build on that collection through subsequent years. I am talking quite expensive crystal here. Not Waterford, but close. Their generosity and good taste overwhelm me and I have been sure to let them know that.
Now here is my question.

I am anxious for this collection to grow to the point that I have enough of it to use on the table at Christmas when these people come for dinner, but, because of the cost, the collection is growing slowly. I am wondering if it would be alright for me to purchase some of this crystal myself, to fill out the set quicker, or if that would be the wrong thing to do. If you advise that it would be alright for me to do that, how do I let them know what pieces I might order for myself so that they don't duplicate those pieces when they purchase on my behalf?

As eager as I am to amass this collection quickly, the last thing I want to do is offend my friends. If you should advise against purchasing for myself, I will, (reluctantly), follow your advise.

Thanks for your assistance,
Dan Coventry