Never pulled, and now Yuzu

Hi to everyone, I'm a 2 months F2P player, never used a single gem since the day I started the game. Now I don't want to mess up, I've got 18k+ gems, and I would like to know:

should I go for 2 Yuzu for the discipline, or it's better 1 Yuzu and her signature weapon?

and what about the hairpin everyone's talking about?

Ty :)