This is a very very good idea. Buying fragrances is like buying jeans for gifts. The chances of getting it right are... you knowI'd suggest sample sets. Perfume is weird, scents react differently to each person's skin.
I agree- the candles are divine. Or try Diptyque candles- they make a very welcome gift. I find giving cologne/perfume tricky- some people cannot wear fragrance or it has to be a very particular brand/scent. It gives them a headache (like me .I agree re. perfume reacting differently to different people's skin. My favourite Jo Malone scent is the intense cologne Dark Amber and Ginger Lily.
What about home fragrance instead? I love their candles. I currently have Pomegranate Noir and Wood Sage and Sea Salt.