I. Breeding success: Hope torches, and friends to light them, are the only way to improve your odds of getting the more difficult monsters. Well, that or spending real-world money to get diamonds so you can just buy them or speed up your attempts. Do you have torches, and have you added friends? I can say more about this if you have worries or aren't sure how it works.

II. Leveling up to get monsters to Shugabush Island: This you can do on your own. I don't know how much you have already figured out, so I'll build up from the basics.

• Leveling up requires food
• food requires money and bakeries (which also require money)
• money requires high-level monsters
• high level monsters need a place to sleep (bigger castles)
• castles need diamonds and gold to build.
• Diamonds are the hardest resource to come by without spending real-world money.

So, in order, your plan should be:

1. Build a "maximum mine" on Plant Island as soon as you can. This gives you 4 diamonds/day. Build mines on the other islands as soon as practical - they each earn an additional 1/day.
2. Get some 3-element and 4-element monsters on each island you have open. This might mean selling some 1 or 2 element monsters to make room, but always keep one of each type if you can. The advantage of 3 and 4 element monsters is two-fold: they earn gold at a higher rate, and they can hold more before they are full. With nothing but simple monsters, waiting 6 hours to collect gold gets you no more than if you waited 15 minutes. With more advanced monsters, you can wake up in the morning and have much more gold waiting to harvest.
3. Diamonds should always go to improved infrastructure first. That means, better castles, better breeders, better nurseries.
4. Money should be split between food production and better infrastructure.
5. Food always costs the same in money - what you can control is time. There are two approaches to faster food production: Bigger bakeries, and more bakeries. More bakeries is a valid approach. Decide how much you have to spend right now on food, and split it evenly as you can among the bakeries that you have built.

That's the basics. If you can give us a summary of your current status, I'd be happy to give more specific advice! What level are you, which islands, what structures on each, which monsters?