Sounds like a stupid question, but what grants XP to your guild ?
PVP trophies affects league rank. League rank defines gold bonus for login reward.
Filling tasks grants those little color stars. Those level up statues levels. Statues levels raises magic mastery and unlock bonuses.
What does increases guild experience points ?
Guild experience points raises guild level. Guild level affects maximum number of guild members. (up to 30).
What else ?
What's the benefit for leveling guild beyond the 30 player limit ?