The empire that has similar characteristics to this kingdom, is the Gupta Empire. I recommend adding roads that encourage trade throughout the empire. The roads will take place of the trade routes and many more traders will take advantage of the roads causing more riches from faraway countries, or lands.

Gupta built roads with the intent for it to be safe and comfortable for the traders, and travelers. p.80

Kiana-Scenario for Raja #2 (Economy)

The roads of the Gupta Empire allowed traders to move easily form city to city, and it also moved goods to important waterways. The roads also let the traders know where they were going, and built better relationships between cities in trade. p.80