If you're in a warring clan, get 1. dragons 2. level 3 spell factory 3. 200 troop spaces
Your first lab upgrade should be level 2 dragons. Offensively, dragons are the only thing that really matter for war attacks for TH7, no matter what you do defensively as a 7 you're probably getting 3 starred to any decent clan, but if you do what I mention with dragons you can at least contribute 6 stars to the war effort. But seriously, for defenses, until you have both your AD's maxed they'll just pummel your stronger one and you'll be left totally defenseless no matter what, so for wars, it's a futile endeavor to weaken yourself offensively to try and upgrade your defenses when you're guaranteed to get 3 starred either way.
If you're not doing wars, it really doesn't matter.