u wont need a prolactin antagonizer on a test only cycle , u would only need that when running a compound like tren or deca because they are 19nor's . Yes u will need arimidex , and test only because it is your first cycle and u need to work out how your body reacts and responds to just a test cycle , so in the furture if u run more cycles and have problems , u will know and be able to pin point which compound it is . also test only is a great cycle on its own