One key is to disband your navies, and perhaps some of your starting army (notably Cavalry).

Many factions that aren't rich or populous to start out with (which would entail Carthage, Ptolemaic Egypt, Romans, and Seleucids, and perhaps Bactrians) will soon plummet financially without some prompt expansion, and judicious use of the starting 5,000 mnai to build roads and other economical upgrades in their starting provinces.

Barbarian cultures in-particular have a problem it seems, but so do the Hayasadan, and Pontos.