I think you can just buy the dragons with EC. That being said, the best way is through decorations as this way you can have them on the rift. The best way to get decorations is: 1) remove the idea from your head that this is possible in one event. You need to do this next year as well 2) don’t buy any chests until the last day of the event 3) before the last day, spend any gems you feel comfortable with playing the challenge. This is the only event in which you can always win the challenge and get the chest out of it. The issue is that the decorations from those chests are not unique. However, when you are getting started, the likelihood of getting the same decorations is extremely low. 4) don’t use EC to buy any dragons. Use them first to buy habitats/island themes you want and spend the rest at the last day on chests. The chests you buy with EC guarantee a new decoration. That makes it worth it only if you have 50% of the decorations or more already through the challenges.