hottopic , Depop, cupcake cult , vampire freaks , skeleanimals , silent scream clothing.
you can get skinny jeans/belts from your average clothing/department stores like Walmart, h&m , American eagle and such
DiY is also good. If you have any plain long sleeved clothing, you could try ripping up the sleeves to make them look cool or add tassels to the sleeve ends, or try buying fabric markers so you can draw stuff on it