Sacrifice events comprise of two parts.
First and foremost, you get additional rewards from sacrifices, and that’s already a good thing.
Second, you have challenges to meet while sacrificing (ie : sacrifice X essence value, reach Y tier sacrifice) that will give you additional rewards.
The best part is those rewards are usually sacrifice worthy themselves, and for great essence value, starting a sacrifice loop that will continue until you run out of resources or patience.
Planning for a sacrifice event is done in two ways. First, you need inventory space, so think back to the time when you increased inventory only to store new useable toons, but realize that now you need more space than that. Spend the gold or ironite to do it and it will reward you.
Second, you need toons with good sacrifice value. As previously said, several rules govern the essence value of toons, learn them and you will soon be doing incredible sacrifices.
Coming from Vortexes (when you fill the purple line around the sacrifice pit), the Alchemist frags will end up giving you the alchemist, a great toon for mid to high level play.
Once you have him, his souls become a source for frontier coins (much like the lillith souls from LOL events) and a good sacrifice ressource too. Keeping an Alchemist or two ready to sacrifice at all times can be a great start for the next event.
So, do yourself a favor and plan ahead for the sacrifice events. These are usually some of the most enjoyable events for many players, but you'll want to make sure you have gold and souls ready well ahead of the event. It's not unheard of to use up 20 million gold or more.