First things first. Come look here at the rewards you can get for merely owning Summerfall and exploring it: Summerfall Event
“How do I help unlock the rewards?
To earn the free rewards for yourself and your fellow players, simply explore the isles of Summerset and Artaeum and earn the Summerset Pathfinder Achievement (you can find details on the Achievement in your Journal). When an account earns the Summerset Pathfinder Achievement, you (and everybody else) is one step closer to unlocking the next reward!”
So as I understand it, all it takes is to have the Pathfinder achievement, which you get from visiting places. Perfect time to go explore. I really do suggest you use Destinations add-on for that, as ESO itself always encourages people to use them, and create them.
And then second things second. Hollowjack crates are here! And they’ve got pretty marvelous stuff within. There’s costumes, pets, mounts, very unique ones that make you pop your head off and into a pumpkin, no joke, and even skins. There’s a black rooster for a pet, and there’s house decorations that I greatly love, but am not sure if I’ll get them. Definitely better than the last set of crates, even though I didn’t’ get anything good so far. All those gems from reward crate junk really did come handy!