Property ownership & divorce rights.
Property ownership is fundamental, and will precipitate other important benchmarks of equality, like voting rights. A striking example is women's suffrage in 1790s New Jersey. Their state constitution (via absence/use of gender pronouns) implicitly, and later explicitly, allowed women the right to vote for about 2 decades overlapping the end of the century. Why were women there allowed to vote? To cover the eventuality that a widow, left in possession of her late husband's property, could have a say in the election of local property tax assessors. Keep in mind that the US did not give women the universal right to vote until 1920, over 100 years later.
Property rights would help prevent financial insolvency resulting from heirs taking property-based inheritance and leaving the widow destitute. Financial security could lead to further opportunities -- if nothing else, the possibility of an increase in time and resources, which could be dedicated to a furthering of the women's rights movement -- a snowball effect.
It would be hoped that the right to hold public office would inevitably follow -- probably first as a matter of necessity in smaller communities where the number of age- or social-class-eligible males was limited (perhaps as a result of depletion from war fatalities incurred via mandated military service).
Divorce rights are also crucial. Allowing women to unilaterally seek divorce can result in a whole bevy of implicit rights -- the right be safe from physical violence, the right to bodily autonomy, etc. Divorce rights would probably be an easier pill to swallow for the specified society's time period than full-fledged marriage rights (defined here as "the right to choose your own partner") -- but it's reasonable to envision them coming to pass as well, once divorce rights are on the books.
The right to re-marry would be crucial in a society where limited job prospects could mean financial dependence on a male spouse. Marriage rights could mean control over a woman's dowry, which would potentially give them financial independence. Acknowledgment by the state that a woman's basic needs must be provided for could either result in an acceptance of their employment at jobs they'd been previously barred from holding -- either that, or a provision in the divorce law that stipulates, say, continued financial support until re-marriage (which would still be a win).
My grasp of women's rights history is tenuous enough that I am unaware of a possible "chain of causality" that would lead from property or divorce rights to labor rights (defined here as "the right to work in a wide range of possible occupations") but my instinct tells me that a plausible one exists. It would be hoped that as technology improved, reproductive rights would likewise follow divorce & marriage rights.
In a social climate unfavorable to the outright equality of women, your political capital for enacting change will be minimal, so it's important to choose carefully which rights you grant. Go for the ones that are simultaneously the most justifiable & the most likely to result in an eventual domino effect of legislative change.