Style.

Recently my boyfriend has started to dress really nicely. He looks so handsome and clean cut. Well, it made me realize that I would like to start dressing nicer as well. My problem is I don't know what styles I would look good in. What types of clothes that I should buy that aren't too dressy but something to look good in. I'm lost and am  in need of advice. I'm going to be 21 soon and I want to start looking more my age rather than wearing yoga pants and goodies on a daily basis. So, any advice would be very much appreciated. I want my boyfriend to look at me and say, WOW! I want to look sophisticated and stunning. I just need someone to teach me how!