Casual, I usually wear jeans, t-shirt/polo shirt/short-sleeved shirt, leather/adventure belt, and sandals/adventure shoes
Formal (attending uni class), I usually wear jeans/pants, polo shirt/short-sleeved/long-sleeved shirt, leather/adventure belt, and adventure shoes/boots/leather boots/slippers
Very formal (graduation, wedding party), I usually wear suits (without tie for wedding party), batik shirt (for wedding party), suspender, leather belt, and leather boots.
Fashion wise, I prefer very formal ones, but comfort wise I prefer casual ones.