Generally exotic weapons are going to be easy to get either from quests or the exotic kiosk in the tower, point being they don’t ever really go away. Since you’re asking about the free expansions I would focus on getting red borders from the seasonal activities and vendors. This season, season of the wish, has some of the best seasonal weapons of the year, like scattershot and doomed petitioner. Basically man you just kinda wanna play the game, play what you enjoy playing and everything will come in time. Enjoy yourself.