I find that the Seleucids get slaugthered in the early game on all difficulty levels.I have given them 150,000 denarii to start with.I have edited their starting troops and leveled up their cities and they still fall to the Egyptians and Parthians.Along with Carthage they are my biggest dissappointment.I like to ally with them and attack their neighbours to allow them to grow because they really are very powerful when they get up and running.