Welcome to the area and to WNFF. Sorry for the overnight delay on approving your post (We approve firsts as sort of a bot and spam check).
Are you driving down from the northeast? Then picking up the green line at Greenbelt is pretty simple and direct to the ballpark. I think the Glenmont / Silver Spring portion of the red line is going to go through a shutdown some point this summer so that might not work even with shuttle buses. IF you are coming in from Annapolis on Route 50, then picking up the blue / orange / silver lines New Carrolton or Largo becomes options. Those would involve one metro line switch at a central station, L'Enfant Plaza, and picking up the Green line to the park/ navy yard. When you do the switch, you just have to be sure to catch a green line as there is a second line (the Yellow) that services the same platform and will take you out by the Pentagon on the wrong side of the Potomac.
I don't consider the metro bad and take it home from games when I don't bike. Metro has its issues, so I'll let others pipe in on driving tricks.