For Jughead: Wear a dark T-shirt, an unbuttoned plaid shirt in darker tones, jeans, black boots, and a gray hat (that looks like a crown, preferably). If you're feeling creative, you can also wear a leather jacket with a snake stitched on the back.
For Betty: Wear a tight sweater with a white collared shirt underneath and jeans. Pull your hair back into a perky little pony, and plaster a smile on your face. Bonus: you could be "Snake Dance Betty" and rock black, lacy lingerie underneath a baby blue button-down shirt and light pink skirt.