“L” is perhaps the greatest detective alive. He has solved every case. But the reason people love L is for his eccentricities. He never sleeps causing dark circles under his eyes. He eats too much sugar thus he can’t sit normally.
The great thing about cosplaying L is that the costume is pretty simple. You probably already have a pair of slightly baggy jeans; here’s a similar light grey long sleeve shirt. Make sure you get the dark circles under the eyes and of course, the hair. If you don’t have hair like that, here is a good L wig.