What can I do to increase my chances in the Colosseum?

Doing better in the Colosseum nets more gems, more coins, and more XP - so naturally I want to perform as good as possible. Unfortunately, I have no idea what I can do to improve my chances. Should I choose a dragon aligned with the event, or opposed to it? Does level matter? Are hybrids or rares judged differently than the basics?

Level your dragons. Dragon level appears very significant; my level ten dragons only occasionally won Gold medals and often won Silver or even Bronze ones. Using level 15 dragons I almost constantly get Gold medals.

I'm not sure to what extent dragon type matters, and the Wiki is very wish-washy about it. I always make sure my dragons match the element of the event and they almost always get Gold at level 15. My Panlong dragons appear to do particularly well, I've suspected Hybrids do better but Level is the only thing I know matters.

The best way to increase your odds at the coliseum is to use level 20 dragons. They win gold EVERY time. Getting dragons up to this level is very expensive, but the cost can be minimized by leveling up dragons comprised of multiple elements. For example, you only need enough food for one Panlong dragon in order to win every water, earth, fire and air competition. With just a few similary versatile dragons--such as Paper, Century, Love, Butterfly, etc--that are wisely chosen, you can win all coliseum competitions.

I adopted this strategy before some multiple-element dragons came on the market, but I was able to cover all of elements involved with Panlong, Forge, Paper, and Quake.

Now start saving your food for making level 20 dragons!