ideally, the guy should do most of the gasto but if the guy is financially-challenged then, the best (and the only way for him to retain his ego and self-respect) way is to do it fifty-fifty (50% for each person in every expenditure together).
under no circumstance should the gal do most of the gasto most of the time kay this carries the impression that the guy can not support the girl (that he presumably loves) and their family (kids, etc.) when the time comes. (why should a woman marry a guy she knows to be inadequate for a father figure?)
plus this puts the girl in a bad light kay she gives the impression that she is desperate and taking the role of a sugar mommy!
this is a point of view from a guy!