I recommend reading the entirety of the CYOA before you start making choices.
Because the way this whole thing is set up is probably confusing, I’ll summarize the general idea of how it’s meant to be played:
1. You set up what your role will be, the general setting, and how everyone else is going to cheat (it’s not a Holy Grail War without everybody finding an exception to the rules or outright breaking them).
2. You set up your 6 pairs of enemies (or maybe 7 if you’re a bad enough dude/14 if you’re a clusterfuck-trainwreck kinda guy), as this is your main way to gain points. If you want to summon an overpowered Servant or have a special snowflake ability, you must be fighting against other overpowered Servants and special snowflakes in the first place. I’m at least trying to maintain a semblance of balance here.
3. You use the points you’ve gained to set up yourself, whether you’re a Master or a Servant.
4. You use the other kind of points you’ve accumulated to set up your partner, whether they’re a Master or a Servant (assuming you have them at all, of course).
5. You go to sleep and wait for the CYOA to become a reality when you wake up.
Alternatively, you could set up only yourself if it’s one of the predetermined scenarios or multiplayer with other Anons.
This CYOA is nothing but a glorified Holy Grail War generator, essentially.