Lord Shadow
General
How's that a problem? It's normal to lag behind the AIs at first on higher difficulties, since they start with extra units and all.I can't figure it out but I've been playing on King trying to get better but the other civs by turn 30 already have 5-10 military units, a second city, and are sometimes taking over a CS.
But as a human, once you get some cities and developments going, you can quickly catch up and overtake them.
Just make sure to prioritize some semblance of a military in the beginning to keep barbarians at bay. Don't underestimate them.