congrats. Did you use the gold or silver to catch it ? How many did purple dragons require? What stats did the level 100 purple have?
where do you find water tablets nad nuggets?
4 more purple blizzards and you will have an awesome arena team
personally I would grow it first, e.g. try adding int first, and see the effect against a couple of NPC opponents (fire dragon, wind dragon, etc)
then try defence and see impact. I personally attack blue dragons in the arena with magic rather than physical attacks, as they seem to have weaker spritit than defence,
however if you want him as a front line , then defence is also important.
then respec and see how it performs differently, and then try reborn and develop it the best way you have worked out
unless you play around it will be hard to know the best balance, and I am not sure how many purple blue dragon experts their are