How do gangster look like?

Well, it all depends on what era you are talking about. If you are referring to 20's style mafia gangster outfits a pin stripped suit (NOT a zuit suit) that is close fitting and really clean lines with a tie would be appropriate.

If you are talking about modern gangsters, there would be tattoos referring to what gang you are with (Houstone, Blood) and then the colors if that is appropriate. Some gangs, such as the Houstones, do not have a color but a skyline tattoo of Houston is a must, along with sportswear of the city.