Money for nothing

[Skuda]

During my ongoing Aedui campaign I've found an interesting way to enhance the tight budget. Romans attack me in Bononia almost every season and sometimes they offer Protectorate. So, you should accept it for 10000 Mnai BUT ONLY IF you see they're going to attack you immediately. If they do it, you'll have your money. If they don't, your profit depends on how much you have in your coffers in this moment.

[Rahl]

You could also add buildings to the building queues of your cities and the romans won't get anything as long as you have "spend" most of your money before ending the turn. When you need the money just remove the buildings from the queue and you can invest it in other things.
I did this as Sweboz and had some years peace with rome, helps a lot when you are fighting Aedui full stacks.

[Atilius]

...and your chicks for free.