Guilds are usually supposed to offer cooperative support for its members, but that's kinda hard to do in a game that focuses purely on 1v1 battles. In your classic MMO, guilds are a way to group people together with similar interests and goals and help them find partymates to tackle difficult quests, or give them advice in an integrated in-game guild-specific chat, or maybe provide them with in-game economic or trading support. And there are even sometimes guild dungeons or guild wars that guild members can participate together in.
But here in Alteil, we don't have cooperative gameplay, and we don't have things like trading. So really, the only thing that a guild can do, here, is give strategic advice to its members and sorta... mentally cooperate outside of gameplay. But the problem is, there's really no easy way to do that in-game, because we don't necessarily have an integrated guild chat...
I guess you can get guild-specific forums set up here, but another thing about guilds is, not everyone visits the forums, and the game offers no way for players to apply for guild membership in-game. There's no "apply" button where new players can fill out a form or write up a brief introduction or answer a few questions that are specified by the guild on their homepage for applicants. I think that's really something that should be fixed in order to improve guild membership and make them more player friendly. As it is now, guilds just seem like a sort of community outside of the game itself, for which you have to jump through some out-of-game hoops to join, rather than a community that's fully integrated into the game. But maybe that's just because of how Alteil itself is designed.
I don't completely understand how the whole guild system works yet (I've only just joined one myself (Cath's Fan Club)) but I think it would be a lot more encouraging to have some sort of guild-only in-game mechanic. Maybe something like guild rewards for guild points. Maybe a few extra point cards for everyone in the guild in exchange for guild points? Or a special bonus to EXP gains? Anything like that would really help increase guild membership and cooperation, I think.