Welcome to SH3.
If you start in some of the other ports, you can start off with a Type VII.
I always start in Wilhelmshaven so I don't have to make the arduous route out of Kiel. Then get your butt to Lorient and a Type IX as soon as you can.
If you're lucky you can enjoy a year of deck gunning with the Type IX's big gun. With luck you can wipe out entire convoys. Once the merchies start carrying guns, though...
Steve