Evolving Dratini or Dragonair

Basically:
• L19 Dragonair -> L19 Dragonite -> L22 Dragonite = 114 candies
• L22 Dratini -> L22 Dragonite = 125 candies
• L18 Dragonite -> L22 Dragonite = 18 candies + already has good attacking moveset

Estimating the levels from the IVs puts the Dratini at level 22 and the Dragonair at 19, and your Dragonite at 18, while powering up the Dragonair from level 19 to 22 cost 14 candies, so it's 11 candies cheaper than evolving the Dratini, at the cost of 5 IV points which is almost meaningless.

Getting the Dragonite to the same level as the Dragonair would only cost 18 candies, compared to 100 to evolve it, and evolving the Dragonair might not even get you a moveset you want.

It depends on what you want a second Dragonite for. Example: if you only want to have a DB/DC Dragonite, or a SW defender, then evolve another one. If you're happy with DB/DP but you want to take down gyms even faster, power up the current Dragonite.

Since Dratinies are hard to find I would go with that nearly perfect Dratini for evolve the best possible Dragonite and power both them up slowly. Imo having two 1.5 - 2k Dragonite is better than having one with 2.5 k CP. And if it comes with SW, you can even put him in gyms.

Evolve the dratini and hope for DB/DC or SW/DP. DB/DP is decent but the other move set I mentioned is ideal even though it's not much difference. Think of it this way. DB/DC or SW/DP is PERFECT. It's like a Lambo without a single scratch compared to a Lambo with a little unnoticeable scratch. Not much difference but you know that the second Lambo isn't PERFECT. To me that would drive me f@cking crazy. But that's just me.