Hi - you suggest some nice data sources, e.g. the World Bank or FRED, but the links you provide seems to suggest that we can only use series tied to South Africa.

Can we use *any* series from the WB or FRED?

This makes sense, since these sources are rich in indicators that are well known and in a convenient format. There is also overlap with some of the other sources you mention, but a few nice series reside outside the strictly South Africa section, so I presume the answer is "Yes", but just to confirm ...