First, lets get the basics out the way for anyone not aware of it.
At the moment, Guild coins are accumulated in 2 known ways.
Through daily guild quests - upon individual quest completion, and entire guild completion (if all your members complete daily)
and secondly through 'bean-a-colada' explorer skill which enables the ability 'rarity search'
so with the very few ways to gather guild coins and lack of production of guild coins since there are no buildings for it
it becomes a challenge to spend in the guild market freely
in anticipation of the new guild market and all the available goodies which will be available to purchase - i thought of a new idea for acquiring guild coins.
This involves adventures and running an adventure together with members in your guild.
If the adventure's participants are all from the same guild (by system recognition) I suggest an 8th additional loot slot for an x # of guild coins as additional loot, in an attempt to make guild coin earning more interactive, and still require cooperation between guildmates (on multiplayer or coop adventures). Depending on the adventure this # of guild coins can vary to reward 25% of 25/50/100/200 guild coins or any number depending on the other resources in the loot.
This suggestion also makes it more interactive for guild mates to work together
it involves the use of coop adventures or any multiplayer adventures of 2 or more
BB certainly has the ability to add additional slots to adventure loot - this is evident whenever there is an event with event items being dropped.
Also when sending adventure invites, it only allows you to invite players from your friends list or guild members list. If the system can establish recognition of the members in the adventure to be from the same guild (by utilizing the guild list) it could then function to enable this 8th slot or additional slot that will reward guild coins.
Imagine seeing multiplayer adventure loot such as this with the guild coins drop
If the developers look into, I'm sure they can introduce or add this feature into the game in no time.
The name of the resource after all is 'guild coin' so its fitting to include it as loot in adventures you've completed with guild mates.
Also an additional method which can be limited and entirely up to the developers of BB.
Is the use of buffs on guild mates. Give it a small daily limit such as 10 guild coins or 20 guild coins. For every 1 buff you use on a guild mate you earn 1 guild coin - (Up to 20 per day) keep it simple. You don't have to put a limit but that's just a small suggestion.
My main suggestion for the adventure loot should be given thought and hopefully with enough positive feedback from the player community I hope the developers highly consider implementing this feature soon.