Oh I think I see now, thanks. I'm unable to post my monster box right now but, I think the case is that I'm rather underleveled.
Then I suppose my next question is, what's the best way to feed your main monsters? So far I've just been getting the Carbuncles, feeding them, and then when they're pretty high enough level, I feed them to my mains. But then I also run into the problem of lack of coins. I'm not really sure how to get enough coins outside of the Weekend Dungeon.
Weekend dungeons are the best way. Personally I never had a probelm with coins because at some point I decided I wanted a Dryad so I ran Demeter Forest about 100 times and got so much money from that that I was pretty much set.
As for feeding, what you can do to offset the cost is in addition to feeding the carbuncles, make sure you feed your mains 5 of those levelled up carbuncles at once. So that means feed a carbuncle 5 monsters, then feed another carbuncle 5 more monsters, etc, till you have 5 carbuncles. Then dump all 5 of those into the monster you actually want to level up. It also helps to make sure you only ever feed same colored monters to your carbuncles. If it's not the same color as the carbuncle (or the thing you're trying to level), maybe you could sell it (or save it for when you do come across a same-colored carbuncle).
Of course, here you run into lack of inventory space, so it becomes a balancing act of do you want to spend those stones on rare pulls or more box space. At some point though you'll almost certain need at least 40-50 boxes to be productive.
Also keep an eye out for Coins x2 or Drop rate x1.5/2 events on the normal dungeons. A Coins x2 event is a great way to get level up / feed materials while also getting coins.
Also, when you are thinking about whether to feed a monster to your carbuncle, take a look at how much exp it gives you. Not all monsters are created equal. If it's going to give you 500 exp but costs 1,000 gold, then just sell the monster. Try to find monsters with the highest feed exp / cost ratio.
