Germans are in a tricky position at the start, but have great potential to be powerhouse players. The way I normally play Germans is to have all my available units (leaving a few behind for town garrison duty) and consolidate them into one mass army and rush the Britannian city on the French mainland. Without a beachhead, the Brits are forced to build boats to transport whatever armies they need to invade Europe. Leave a good-sided force at that city for when they come back to reclaim their land (and they will, often), and start pumping out Spear Warbands in your other cities, consolidating them into one or two mass armies, and just rush Rome. If you are extremely lucky with a spy, you can siege Rome and their (often) puny garrison, wiping out the Senate faction in a single turn. If you arent lucky, you are SOL as the Senate's field army will come and smack you down.
Once you have Rome, build the temple that will allow you to recieve the Gothic Cavalry. With the Chosen Archers and Gothic Cavalry (complete with black eyeliner and Cruxshadows CD), you can easily dominate the Roman factions that want Rome for themselves.