I say try to pick a moisturizer that works with your type of skin. I do not have the oily skin problem, so I never had a problem with it. Try to find an oil free moisturizer. And like airline said, pick up rice paper to blot away the oilyness.
A pore minimizer is to make the pores on your face look smaller, so that your have smoother healthier looking skin. About sideaffects, I have no idea. I have no problems with it at all, and having been using it for a year now.