If you're skinny, you need to dress in a way that accentuates your leanness. You can still convey a sexuality and look good.

If you're thin I would say go for a more metrosexual and slightly outlandish way of dressing. Because wearing stuff that would look good on a muscular and athletic person can easily make you look like a cyber nerd in ill fitting clothing and it will make you look unhealthier and even skinnier.

You might hate the idea, but I am lean and I wear tight jeans, v-neck t-shirts and accessorize with necklaces, rings and even scarves. It's all about the self confidence to not give a shit about other people judging you on your clothes. Don't go for an ill fitting polo top and baggy jeans.

In the UK there is a comedian called Noel Fielding, he's quite skinny and not even slightly athletic and yet there are thousands of women who are practically OBSESSED with him. But take away his fame and his dress sense is going to have him catching every eye in any given room.