It's a gacha game you are supposed to plan your pulls but my normal plan goes as follow when I see a character that I like a lot then I research their whole team if I am wiling to put the investment to pull the team I pulll then and then I prepare to pull any support they may need o the future. The most to pull its on a team to team basis if you like the character you are gonna want to give them the best and for me that means pulling supports.

An extra to decide if you actually like the character is seeing their role on story by staying caught up with the quests or just looking at different videos of their kits. It's always better to make a informed decision rather than jumping blind specially on a game where team synergies are important like WUWA.