Mango Margarita Pie with Gingersnap Crust

1 1/4 cups gingersnap cookie crumbs (about 20 cookies)
5 tablespoons unsalted butter, room temperature
3 tablespoons plus 1 cup granulated sugar (divided)
2 envelopes unflavored gelatine
1/2 cup fresh lime juice
4 eggs, separated
1 cup pur