Powering up attackers
I'd like to power up some of my Pokémon's for attacking gyms. I'm hoping the new gym system will trigger me to attack them some more, because currently I'm more of a collecting player. I want to know till what level you guys level up your attacking team. Level 25 or 30 or do you aim for a fixed cp number?
Answers
Your method is probably the most effective one - an attacker at level 30 is strong enough for pretty much any battle.
However, I still like to keep some of my favorite attackers with perfect moveset maxed out (Espeon, Alakazam, Jolteon, Golem, Venusaur, Exeggutor, Gyarados) just for fun. I like using them.
Stopping at 30 is the right thing to do....however I really enjoy having some monster attackers and in regards to certain pokemon, while it isn't the most cost efficient to fully power them up I do anyway.
After level 30 you could bring up 2 common pokemon (almost for the cost of getting one to lv 35.5 (where mine go). But I like having at least 1 super Jolteon (2554) for the multiple Gyrados gyms. If those gyrados are interspersed with Blisseys etc then I like having to have only one Jolt with a cushion for mistakes rather than 2 that are only good for the Gyyrados. This same logic applies to high level Vapes and Dragonites but thse also can be dual purpose mons as they can also be high level defenders maxed or sledgehammer offensive weapons that save space in an attack crew. I also keep a maxed Scizor, Golem, and two maxed Laprases. These are just for fun.
The truth is that while it isn't the wisest move to max offensive mons past 30 it is a lot of fun if you are smart about it and can be advantageous with all of the repeat mons in gyms now.
To supplement these mons I use wild caught 700CP+ eeveeloutions as throw aways. It costs me nothing to maintain those.