If this hasn't been already been said, "don't wear your wife's clothes, without her permission". Even with having said that, go and buy your own stuff. In a marriage you may find a yours, mine, and ours, but why does anyone want to get into any awkward situations when you have the consent of the other to buy your own clothes.
My favourite night wear is a knee length nylon night gown. I prefer Vanity fair for all my lingerie. Go into the stores and get the feel of the material before buying your items. This is a time where having your wife to help you in your selections really coming in handy. Don't get your knickers in a knot! Speaking of knickers, don't buy several of the same type at once. Get a pair or two and check out the feel, but especially the comfort before buying several pairs. It's no fun buying something to only find out that they are not as comfortable as you hoped. Remember to have some fun, you are still the same person regardless of the packaging.