I recently started playing DragonVale World and due to the lack of information there is still i decided to share my current discoveries. This is not a perfect guide but rather based on being easy to follow before reaching higher levels and further understanding of the gameplay. I apologize in advance for not making a pretty layout.
My "spending gems" order:
1. Hatchery upgrade 1 (= 2 spots)
2. Hatchery upgrade 2 (= 3 spots)
3. Epic Breeding Cave
I also upgraded Snackery to 125 food capacity, this is not necessecary however. I'm currently saving for Hatchery upgrade 3, which is 1000 gems. I can also add that I bought 1000 gems with the starter pack, which is why I could upgrade early.
First of all, level 1-6:
Tutorial includes a Fire Dragon, Jungle Dragon and how to combine them. Whenever you get a new type of element, build a habitat and buy the dragon (check times for incubation if you have few hatchery spots). First levels prioritize jungle combination with every element, and then try to get the combinations like Fire and Earth. I would strongly recommend only keeping one of each dragon type and sell if you get more. Even if you got all current combinations keep breeding and selling (though this is seldomly a problem). You will gain exp i 3 significant ways: completing goals, clearing obstacles and feeding dragons. Clear the cheap obstacles first, the more expensive ones will come later and are not very important yet. The primary way of getting exp will however be by feeding your dragons. Buy more farms when possible and plant the 30s crop and the 3 min crop; I spent all money I had left on food, this was a very good idea. Try get dragons to at least lvl 4 (so they can breed) and then continue feeding as much as possible, but prioritize dragons under lvl 4. Eventually you will get to lvl 7, and this is where the fun begins :D
Send dragons to Brightleaf Jungle as much as you can to gather food, and use this food to level dragons. Use the food you grow in the farms for selling at max price (using free ads) in Silvia's trading post. You can also sell the food from Brightleaf, but prioritize selling Mushrooms (or better) from your own farm. This is because food you grow can be sold for more cash and food you fetch gives more exp when fed to dragons. Whenever you can, upgrade Brighleaf Jungle for 5000 so it can contain 5 dragons (and continue upgrade for storing more). Since you prioritized breeding Jungle dragons in level 1-6 there should be no problem with filling it up. Now you got plenty of space to breed some more dragons. Continue using these methods to rapidly expand your park; by earing dragoncash, you can clear, buy more habitats, upgrade habitats (at lvl 9) and get more food. The food you will sell/feed and get more exp and so on. This basic strategy is easy and fills your islands with new options as you level up.
I've myself only reached lvl 9 this far, but comparing with my brother I'm 3 lvls ahead of him, and I started 10 minutes earlier. With this said, I've played a lot of the original DragonVale so I'm rather used to the concept but didn't bother with any complicated start. It is a little bit more than this when you play, but this is the core to what I did. When I level up further I'll maybe write a more strategic guide, but right now I'm checking how breeding works and experimenting with different pairings for a better understanding how everything works. Below is a basic explanation of types of dragons in DV World, and this concludes the end of the Easy starter Guide.
Base dragons - These are elemental dragons, and the basic dragon types of the game. It currently consists of Fire, Earth, Water and Air type of dragons.
Location dragons - These are combination elements, which can be combined with any base type dragon and results in a new type of dragon, for instance "Fire dragon (base type) + Jungle Dragon (location type) = Flytrap Dragon (Brightleaf-location type)". Current location types are Jungle, Desert and Cavern dragons.
Rare Dragons - These are any type of dragon with a subelement. For instance a Water Dragon with a Fire variation. Variations consists of Base elements and are displayed with a round element indicatior rather than a flag.
Epic Dragons - Need special combinations either containing a specific pairing or a specific setup of elements.
Fairy Dragon and Glimmverse - I have currently no idea what rules abides to these type or what kind of dragon they are since I'm not high level enough to obtain them.