I hatched a Magby out of my very first new 10k egg last night, so I was stoked with that! I also finally got enough candy to evolve my Dragonair into a Dragonite. I had two to choose from - a 68% IV with much better CP, or an 82% IV with lower CP. I went for the latter, much to my son's disgust, but I can always get more candy to power up, whereas the IV is set forever.

I don't tend to spend much time battling gyms so I haven't been quite as diligent organising attackers and defenders. I do have a couple with mediocre IVs but a 100% defence stat that would be good to chuck into gyms if the opportunity arises. I need to rename them with suffix A and D so I know which to use for what.

@CutCutCut - you can look up the movesets here - some are better than others, but you won't know what you're going to get when you evolve your Pokemon - it's randomly assigned, as far as I know. However, when it comes to powering up, you can easily work out which are your best Pokemon. Use the in-game appraisal system to work out your IV - your Pokemon's perfection level, which is based on its scores for attack, defense, and stamina. This list will help you understand the rather cryptic appraisal messages (it's different depending on which team you're in, so make sure to click the relevant one). Next, you want to work out your Pokemon's level and IV score. For that, I like Pokeassist. Use your Pokemon's details screen to find out its CP, health points and how much candies it would need to power up, and enter them into the calculator. You also need to say if it's been powered up already. Then, tick whichever of the attack, defence and HP boxes your in-game appraisal says is your Pokemon's strongest feature (there could be more than one). Finally, select the score of that best feature from the 'best' dropdown menu. You get that info from your in-game appraisal. It's the phrase that comes up before the size. Match that phrase to Phase #2 of this chart to find out the score. Then click calculate, and the IV calculator will tell you your Pokemon's IV rating and level. 

Now, if you want a Pokemon specifically for taking down a gym, go for one with a good moveset and and the maximum attack rating of 15. If you have one with max defence stats, that's good for putting into gyms to hold a slot. So that helps you decide who to power up and who to discard. I have a godly Gyarados with 97% IVs and the top moveset, so he's fantastic for anything. I also have a Kingler and a Flareon that have 100% IVs that I power up as much as I can. On the flip side, I once had a Bulbasaur with an IV rating of 6, lol. Hope that helps!