Playing as Shimazu, pulling in over 7k/turn even after building 3 full stacks of troops, another half-stack, and 2 stacks of ships (mostly captured pirate ships). Took over the starting island and began my march to Kyoto. Just got the message the Shogun has taken notice and is plotting against me, so it won't be long.
I've learned a few things this round that's making the game super-easy.
First, try to get the Nanban Trading Port early and convert to christiantity. Aside from the huge economic boost the port provides, once you get a priest out causing unrest in enemy provinces you'll find yourself just sweeping across the mainland. I have a maxed-out priest now who has a 90+% chance to cause unrest. He's constantly disrupting provinces ahead of my expansion keeping a buffer of rebel states between me and my enemies.
Second, get the Chi arts that provide you with better farms ASAP, this is even more important I find than the military upgrades. Aside from the economy boost of better farms and being able to build bigger forts, you also need the extra food for merchant guilds for more money.
Third, get the diplomacy Chi arts as well. It helps a TON. Even hostile leaders will be moderate in reception to trade deals. I'm currently trading with every single nation on the map except for the one I am at war with.
Also, don't forget to check your financial tab once your finally ready to begin your military offensive. Make sure that your income BEFORE TRADE is equal or greater to your military expenditures. I lost my last campaign because I forgot to do this before marching off, only to lose because I had no money once all my trade deals were cancelled.