So are saving the 200-300 Dratini for next double candy event?

I started the event close to 500 candy, evolved 3 dragonite and finished with 650 candy... So, I already transferred them because I don't need them. But your case may be different if you don't hatch dratini very often

Saving them,I never ever see wild dratini

I never have to worry about dratini candies. I have 5 Dragonite that are over 3500cp and I still have 1600 candies. In addition I have 700 rare candies. To be honest the gym system is so weak that I rarely use more than 1 or 2 pokemon to beat a max out gym.