Evolving chansey

Wait or power up the blissey you already have. Not because that Chansey is bad - but because you only have candies to evolve and take the blissey to around 2k cp which probably isn't high enough to not be at the bottom of gyms.

Depends on your area though. Maybe everyone else is barely level 20 and 2k CP is considered high

That is a very good IV split for Blissey.
It will have a much better CP at the same level as your current one.

Good luck with the moveset.

Its IVs are where it matters. 100% are just for bragging.

I had a similar question. I have 2150 11/15/14 ZH/P. And I got one 75% and then 2 84%. The two 84% will evolve into 1800ish Blissey. and I have like 74candy or so.

Didn't know what to do so I did nothing. Anyway that Blissey is already in a GYM for three weeks now.

I'd walk Chansey/Blissey until I had enough candies to power it up to a decent CP level, then evolve and power up in one go. Then if a better Chansey comes along, that can be the one you evolve.

Evolve it 15 attack is ideal for blissey due to her low attack stat and you could just walk your blissey to get more candys trust me its not that hard in like 5 months I walked 170 km with dratini and thats with not much walks