I just finished a DIY postbac at my local state school. My undergrad was engineering so I needed a few prereqs. I took:
Bio I
Bio I Lab
Chem II
Chem II Lab
Bio II
Bio II Lab
Orgo I
Orgo I Lab
Sociology
Psychology
Orgo II
Orgo II Lab
After I graduated, I went to my local state college and signed up for my classes. I've never been eligible for financial aid so I'm not sure if financial aid will cover a DIY postbacc. They signed me up as a "special permission student" and all I had to pay was the in state tuition for the class.
If you are looking at just taking the prereqs, sign up for them at you local community college or state school. If you are applying MD then you might want to check on the MSAR to see if any of the schools you are interested in do not accept community college classes (a good 25% of MD schools will not accept CC credits). If you are just looking for a GPA boost and have all the prereqs, take upper level bio courses (genetics, immunology, cell bio, etc.).
There are also formal postbac programs that many medical schools offer. These are more time consuming and expensive, but they do look better to some schools. Some medical schools have postbac programs that guarantee acceptance into their medical school (conditions apply of course).
You should be ok for MD assuming you can do 3.7+ in your postbac and if your sGPA does not currently hold many credits both cGPA and sGPA need to be atleast a 3.5 for a realistic shot at MD. A good 3.6+ postbac at 30 credits should get your sGPA competitive for DO.
