What is the Best oral medication for face acne?

Best is relative. Isotretinoin is generally considered the most potent oral acne medication but not necessarily the "Best" especially in females of child bearing age. The best is ultimately decided between the patient and their provider.
Depends. If washes, lotions have not worked well, next step for women may be trial of birth control pill. HOWEVER, it must contain a low androgen progestin like norgestimate. Problem with these progestins is that women who use them tend to have more what we call breakthrough bleeding (bleeding when they should not be having their period). Before starting any pill, see & discuss with your doctor.