Reimu/Yukari are very beginner friendly. People call them overpowered.
Remilia/Sakuya. Effective enough if you memorize where to plant Remi's familiars.
Marisa/Alice: Don't use them. They suck.
Youmu/Yuyuko: Not a personal favorite by any means but they are apparently pretty good at covering the entire screen. (Yuyuko that is).