The very first one was Kate Moss I think. But I was so young I can't even remember how I discovered her. Years and years after I totally fell in love with Lara Stone when I first saw her in Vogue Paris in 2006 (the first editorial she appeared in for the magazine), I was like "Wow, who is that girl ? She's like the most beautiful thing I've ever seen !", After that, my interest in fashion moved to another level, I began buying more fashion magazines, etc...
I think Kate Moss, Lara Stone, and Sasha Pivovarova are the only models who really impressed me when I first saw them in magazines.