Which golbat to power up?
I have 3 golbats now:
CP FA SA FAT SAT
1106 bite AC Dark Flying
1100 WC PF Flying Poison
1099 WC AC Flying Flying
FA = fast attack; SA = special attack; FAT = fast attack type; SAT = special attack type. CPs are close.
All of them have good IVs and quite close.
Answers
With Niantic ganking the updates and game tweaks with all their cash, I would expect Gen2 sooner rather than later. Save all Zubat candy to evolve a hatched (2k egg) Goldbat. Anything less than 14/14/14 I trash because you will get many.
Then evolve any Zubat to Golbat above 14/14/14 and save them for Gen 2: In Gen2 Golbat will evolve to Crobat (estimated CP +2.3k)
They say you will need 100 candy for Golbat to Crobat. Worry about the move sets after they are evolved. Its a RNG 'ting, so 4 or 5 Golbats should get you 2 decent Crobats with perfect move sets.
But there are dozens of better pokemon to use against Exeggutors - Parasect, Pidgeot, Venomoth, Arcanine, Butterfree, Flareon, Cloyster, Dewgong, Gengar... just to name a few. Hell, my 1000 CP Raticate with Bite+Hyper Beam just obliterated a 2100 Exeggutor earlier today.
Plus you'll need the Zubat candies for Gen2 so I'd say it would not be a wise decision to power up any Golbat.
I have previously used a Golbat with Wing Attack to train against my ~2000 CP Venusaur with Razor Leaf+Sludge Bomb. It is not an ideal attacker, but is resistant to both grass and poison. After I had powered up my Venusaur well past 2000 CP, I never bothered to keep a Golbat at a good CP to match though.
