Training at Transylvania is a good choice (Studying a class there or reading the books in the library there)
That gives you like 16 xp per day nowhere near as fast as any other stat.
Hmm.. The other way I know to increase ero is by : 1. Getting captured in the deserted base and purposefully getting toyed with by mystra (Don't overstay or you'll get a bad end)
Or
2. Doing dance's in the desert sunshine town brothel
You could also combine the dance's in sunshine and new ark city to increase ero but I think they give the same exp nonetheless
