Wantgender is a form of genderlessness where one wishes to have the feeling of gender, or where one wants (to have or to experience) gender even though they do not possess gender. It is a broad term, stretching from wanting one specific gender to an unlimited number of genders to wanting any form of gender, no matter the type.
For example, there may be an Agender individual who wishes to have a connection in their gender to Masculinity, even though they feel more genderless and Feminine than Masculine. There may be a neutrois individual who has no recollection of ever having gender, so wishes to feel any form of gender. Or someone may be questioning their gender and this is the only thing that makes sense, for they wish to be pangender but do not feel that way.
Like stated above, this term can be used very broadly to describe many feelings of gender.