Saving Primogems

All the characters are so appealing that I want to pull for all of them, but if I do, I won't have enough Primogems. I try to consider the following points when deciding whether to pull: ・Is it really necessary? When a new character is released, I consider if my existing characters can suffice. For example, Vourchanka is cute, but can't she be substituted by Xingqiu, Yelan, or Furina? ・The featured 4-star characters I've already max-constellated (C6) Diona and Faruzan. If I pull and get duplicate 4-stars, I feel like I'm losing out. Of course, if Lisa's voice were to say, "It's not that I need you because I love you; I love you because I need you," that would also be a valid point. I'd love to hear everyone else's opinions. Sorry for the long post.