Well, to level up (or get allies), lots of bucks are required. In early levels, I sold any core resources (not everyone is allowed to so, it seems random which you can and can't), but after a few levels, you need energy more than anything else (energy needs = population* level). Since bucks/cycle = asset production + (population * level), more people = more bucks (but more food and much more energy required). Bliss I ignore, since buying stuff raises it and if it is much higher than needed, you just have to pay more to get rid of whacks. Keep a bit of surplus, just to take any bliss hits in case your energy is too low for a cycle (otherwise, just keep adding energy -- at level six, it's all I spend surges on now, while I wait for enough cash to level up). Had I had a strategy earlier, my population would be higher and I'd be growing levels much faster (not that I ever hope to hit the levels of some early alpha players).
I'm almost to the point that it costs as much to join an alliance as go up a level - with the doubling cost/ally, I may never make it to twenty... although, I am getting close.