devil-may-care
raffish
rakish
marked by a carefree unconventionality or disreputableness
a cocktail party given by some … raffish bachelors
Crary Moore
carefree
freewheeling
happy-go-lucky
harum-scarum
slaphappy
cheerfully irresponsible
carefree with his money
freewheeling urban youths
had a harum-scarum youth