What to prepare for?

Camelot was quite difficult even for some veteran players but thanks to many warnings most masters were able to prepare to it beforehand and now, I would like to know what else to expect from future events or singularities and what to prepare for them? Like save some fp(like it was with angra, whom I didn't pull), or grade some specific servants.

Nevermind the summer event, I already prepared smh for it.