I can't recommend buying slow primes, however cheap.
Why not? There is nothing inherently wrong with less fast prime lenses. For example, I think the Sigma 30mm f/2.8 is a stellar lens, which is probably made possible by the not very large maximum aperture of f/2.8.
If they would have made it faster, it would have required a more complicated optical formula with more compromises, and, worse image quality.
The first prime you get should be the Olympus 45/1.8. As nice as the 60/2.8 is, you will find it long indoors and slow in low light.
Both of these lenses are good. The Olympus 45mm f/1.8 is not very good wide open, in my experience. For the best image quality, I would stop it down to f/2.8.
The Sigma 60mm f/2.8, on the other hand, is very sharp already wide open. See, for example, this comparison:
Both lenses used here are designed for a larger sensor than in the cameras pictured: The Sigma 60mm f/2.8 DN used on the Olympus E-M5 ...
m43photo.blogspot.com
I would not be afraid at all to use the Sigma 60mm wide open at f/2.8.
I do agree that the Sigma lens is a tad long, though. But in many cases, it is just as usable as the Olympus 45mm.