A Simple strategy
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Quite simple, try to have Abe before you enter, borrow one from your stronger friends is a good idea everyone can do.
Then, inside, pick your easier battles first, look for the lower levels opponents.If you're new, don't use fast battle option, observe the battle carefully. When things start going south, quit the battle to avoid losing key characters, you won't even need to use heal or resurrect points if you play this right.
When you got the chance to pick helper characters, pick one that synergizes best with Abe, maybe Kate, Magna, or Michonne.
The best buffs are ones that raises attack and defense, splash damage and 100% random damage. Speed up is also good when you don't have Magna. Charm front line is another good option if you're not fast enough. Lifesteal is another good option when available.
In battles, switch around your Kate and Abe to take out most dangerous opponents first, this would be Guide, Sebastian, Jeff, and Sherry. You see them, eliminate right away.
After several retries, if things keeps going south, quit the event and raise your stats, collect and raise more survivors and gears first outside, don't end the event. Come back when you're stronger.
Try to save all the healing points and use them only before final fight.