As someone who bought a used Benz for a first car, I can tell you maintenance costs are outrageous. Oil changes were at least $75, and because they are foreign cars, parts will be expensive. They also require premium fuel.
Take a look at average maintenance costs for the 328i, and see if you can stomach them. If so, go for It! Otherwise, an economical car isn't a bad way to go. You'll have money left over for maintenance or modifications.
Good luck to you.
Former Mercedes owner. (1995 C280)