First see what is offerred for the Summer session. There are many classes that may not be offerred. How many classes do you plan to take? I would either start the Math series 21A and an English Lit class/Comm 1/3 class or Chem 2A and one of 2 I have already listed. Chem 2A would be dependent upon the Professor. If Prof Enderele is teaching, definitely take the class. Chem 2A is also a major weed out class for Pre-med/Bio majors whom usually take in the Fall quarter, so if you can get that class done this summer, you will be in good shape or wait until Winter quarter.
Here are the GE requirements for UCD: http://catalog.ucdavis.edu/ugraded/gereqt.html
Cultural Anthropology is a good GE since it fulfills the Cultural diversity GE, along with Writing and Social Science (known as a triple dipper).