This may contain SPOIERS...ye have been warned...
Gatherings seem like a terrible idea. They real do seem terrible.
You must be thinking "well, PetTheDog, what makes you think that? You've only been here for an hour, how DARE you start making such big accustions!"
I can explain.
Gatherings are supposed to be all fun and games but really they aren't. Discusing these tactics has led to fights between cats and territory. I don't remember in which book but it is revealed ShadowClan leader said a lot about the struggle with prey. And he was attacked for it. "PetTheDog, when did they fight over Sunningrocks because of a gathering???" you might now be asking. I can explain that one too. They accused each other of stealing prey and driving out RiverClan cats, thus making ThunderClan cats angry and anxious. After a while it did lead indirectly to a fight.
And then, Swiftpaw anyone? Yeah, Swiftpaw, we all remember him. The ThunderClan apprentice with high hopes for warriorship. He told ShadowClan they where housing Brokentail. This led to - yes you guessed correctly - an ambush.
And then, when ShadowClan took on all three Clans and tried to kill everyone at the Gathering !!! They where punished by StarClan but overall it did not improve anyone's relationship with ShadowClan. In fact, ShadowClan was shown to be angry at ThunderClan for "killing" their leader.
Overall Gatherings sound like a bad idea...