Build then re gain you money but allies keep making money. Build more then you can waste all your money on something stupid.
Put all your gold in allies, unless you already have a good amount there. If you already do, upgrade.
If you are in this game for the long haul, try to upgrade by purchasing land. Getting more land with a maxed building will increase your plunder by about half a million per hit, and your gonna do a lot of hits in this game, so the sooner you expand your territory, the more cash you will earn. It's expensive It's a grind It's worth it
Do what moose said - dont do quests unless you want nobility, crystals or achievements. You have all the time to do those and not so much to grow