I was thinking sts could add levels to a guild. Right now there isn't anything much that makes a guild unique other than the players in it and whether there is a guildhall or not.

What I propose is that for each guild level players in that guild get perks and benefits (maybe like 10% off pet feed cost or something) as the guild levels up the perks will be better and have more use. As for the way you level up the guild I was thinking that it shouldn't be gold related but rather with specific items (level 1 guild = 50 cracked nature and 50 cracked water jewels). The required items to level a guild would be a guild effort as everyone will be able to donate to a donation box somewhere in the guildhall.

Along with this some events could have a guild score. Just like how players can accumulate a score in an event, the score of a guild would be a total of all that guild members scores. This would add some competition between guilds. Whether or not there should be guild rewards, I'm not sure.
However IMO for this to work there should be a cool down for a player to join a guild after leaving another guild.