Hello,
It's a bit hard to say which ones are "easier" to obtain than the rest, mostly due to the fact that you have to be placed at least 3rd in a fansite contest, which is not always easy. It depends mostly on the amount of people you're competing with and how often that fansite organizes events. With that being said, I would recommend that you look up at another question posed here in TibiaQa a few years ago (1), regarding the prices and availability of each fansite item. The logical association is that the cheapest the item the "easier" to obtain, but still, that doesn't mean that it's as "easy" as just waiting for a simple boss to spawn and hoping to get the drop.
From personal experience, I've been participating in different contests since 2023~, and I managed to get one fansite item, the Epaminonda's Doll, at the same time I was never placed above 2nd place, it's not that simple. Keep in mind that you can also get some unobtainable items even if not a fansite item, such as Blue Sphere, Yellow Rose and other rares.
Good luck on your search for fansite items!
(1) https://www.tibiaqa.com/4335/what-is-the-price-of-items-that-are-given-in-fansite-contests