Yes, firstly, don't overdo it with too many ETFs. Just pick a few core ones and stick with them. Otherwise you just end up with higher costs, duplication of stocks and possible over-exposure to certain stocks that is hard to control.
Secondly, pick a good mix of local, international and property shares to spread your risk.
If you want to stay with Satrix only, I'd recommend something like the following portfolio split:
Satrix 40 (STX40) : 40%
Satrix MSCI World (STXWDM) : 40%
Satrix Property (STXPRO) : 20%