Bear in mind that with negatively geared properties the number you can hold is lower than with positively geared properties. Also, you are making a loss on negatively geared properties, so if you want to take that path you need to make sure you have a strong likelihood of good growth in the medium term (at least). With positively geared properties, though, you may not have as much capital growth, but you can effectively hold the property at no cost while waiting for the gain (and pocketing some cash in the meantime).
I try to buy properties with good short term capital growth potential, that are either positively (or neutrally) geared at purchase, or that become positively geared within a short period of time.