It's flattering to consider me to give you an advise, but i'm not expert with that.

But i'll try in anyway i can... I can't tell you how much dragons needed by just looking in your island, it's hard to count the elements in it and as you say there are more inside the hibernation cave.

You can see how much more dragons needed in each element by touching the shrine statue, the dragons inside the hibernation cave still counted and even if you sell the dragon after the purchase of shrine. I suggest you feed up the dragons that have 4 or 3 elements in it like panlong, bloom, love, sakura, all the elements in them will counted on your shrine. If you don't have them, feed 2 elements dragon.
And for money making, rare dragons like rainbow, sun and moon are good money maker. Other strategy is to fill up your island with panlongs as much as you can in an earth habitat with fire and water boost. Another is by breeding and selling eggs of iron or magnetic for quick income.
"This game is simply the power of LUCK! Oh, and MAGIC FINGER!" GC id: kryp2n8