Is this Dragonair worth evolving?

Kind of. If the candies are rare for you (I've inferred they are) then this MAY evolve into something you can use on defense in your area. Outside of him getting a good defensive moveset he could get a great offensive moveset and you are quite a few candies ahead. It's a roll of the dice but I'd toss them tbh.

i would try my luck.

With IVs of 15/15/7, he will be rather good in term of future CP. I think he is worth spending your 100 candy and more if he has a good moveset.

It would save 53 candies compared to evolving and powering up a hatched dratini. If you evolve the 82%, and then hatch a 100iv tomorrow, you would not be too far from evolving that one too.

I hatched a 95% IV Dratini yesterday. I evolved and it got SW/Hyperbeam. My second Dragonite with those movesets. I then evolved another Dratini with 85% IV and it got DT/Outrage. Moral of the story; just because it has high IV's it doesn't mean it's going to have great moves.