Are you playing peacefully or warmongering? If you're warmongering, Monarchy is a really good bet, since you get free unit support based on your towns/cities instead of having to pay the upkeep costs. If you're playing peacefully, Democracy is usually the best. You might need to reduce your number of units, but most likely increase your revenue capacity. Marketplaces are wonderful for this, as they generate extra commerce and increase happiness at the same time. Also, be sure to road any tile being worked by a citizen.