I've been play spiral knights for over 700 hours and have not found an answer to this question.
-no one seems to care or talk about it
-doesn't seem to affect gameplay
-I'm I missing out on/not getting a large chunk of the game?
-why should I waste minerals on it when I can just craft pet food and sell it for 100 times more money?
Shortly before release (if I recall correctly), players were given the ability to affect gate construction, as a small nod toward player-constructed content. The system was subsequently tweaked a few times. But then missions dramatically weakened players' relationships with the Arcade. (Heck, even the Auction House did. Before that, people used to gather in the Arcade socially. Now they gather in the Town Square.) And using minerals for sprites wrecked the gate system even more.
But, as Juances' link points out, the game developers know all of this, and they are starting to think about how to revamp the gate system, to make it interesting again.
I haven't dived into the arcade in a month, except to see what compounds were. Missions definitely killed the arcade. In the old days, gate construction was hugely important because it determined what kind of levels you had to face before you could do FSC. If someone put fiends in strata 5 on the FSC gate, that meant you had to clear dark city to do FSC, so for that week the number of crowns entering the economy would be lower, as Dark City was merciless toward less skilled players and to an extent acted as a sort of barrier.
I don't expect them to ever go back to a system where players can actively troll each other to that extent, since the game is made to be very casual and easy now, but the developers are working on making gate construction meaningful.
I have good memories of only picking up purple minerals, the depositing a couple thousand into 3 seperate gates making all the lower depths fiends.
I <3 fiends :)
Now it's just the blue and green garbage left over from sprites - a lot of freeze levels lately.
I remember when I would pour out all of my purples into the t2 depths. This was back when candlestick keeps were actually a challenge.
I may do a purple dump for the hell of it. I don't have a Maskeraith to feed.
Well, it used to have a purpose. It used to mean something. It used to shape whole worlds. It used to be our guide to mysteries of this bizarre planet. It used to be our key to the Core.
Now it's just another of those mechanics that they've broken by updating everything else.
Otherwise, Bopp is correct. You can drop minerals into the gates to influence the strata thereof. You're not missing out on a large chunk of the game.
http://forums.spiralknights.com/es/node/89218