I'm fairly new at this myself, but I've been trying lots of frags. At first I was doing the cards, and that was helpful, but on the skin is better. I have rejected some frags offhand on the cards, only to find out later on that I actually liked them. I figure I missed the drydown as well as the interaction with the skin.
The thing that brought this home for me was trying Angel, which on first shot was a shocking blast. But then the drydown went through at least 4 stages for me, and was excellent. So if I went by first impression, it would have been negative.
Of course, if you spray the skin, then the problem is that if you want to try several things, you run out of wrists pretty quick. One time I did both sides of my neck, both wrists, and in my shirt, as I recall. That could get pretty funny if you continued by pulling up pantlegs, spraying in shorts, etc. I know, I'm nuts. I was in a store the other day and there weren't many cards around. I ended up spraying each finger, getting 10 samples, as it were. Not ideal, but kind of fun, and I did get one keeper!
Still, the cards can be fun. I will start carrying a pen so I can keep them straight.