You MUST keep your people happy, otherwise you can be elected out of office, the military could stage a coup', or you subjects could rebel and force you out of office. You can focus your economy on a variety of different industries. The base of your ecomony is your farms. You can farm Corn, Sugar, Bananas, Papaya, Coffee, etc. Of course, what may be good ground for corn may not be good for sugar, so plan accordingly.
Some industries are dependant on specific crops.
For instance, in order to run a Rum distillery, you must grow sugar. Besides farming and industry, you can also base your economy around tourism. You can build hotels, restaurants, cabarets, spas, etc. Build a luxury hotel with a spa and nightclub. Build a cheap motel with a pub and cheap restaurant.