The Eastern Empire enjoys a much easier start but the West can be brought down to control very quickly. destroy all barracks except Rome and Ravenna, and then let all the settlements rebel as they pleases (not all at once). Without barracks the best troops they could train is merely peasants and should be dead easy to recover you lands. Exterminate population brings income and stability. Then you could face external dangers. The Western Empire gave me a fright at first but after reading a couple of guides I gradually learnt how to deal with it. It's not that scary after all.