Eesh, this is an old thread!
For skincare help (all types) hit
http://gardenofwisdom.com - Markey (she owns GoW) is an angel and will help get you sorted.
I ended up using Silk Naturals for MMU, cos it's very sheer, doesn't cake on me, and doesn't turn my normally almost non-existent pores into craters. Silk can be good for both dry and oily skin, and if you have a reaction to that, there are a lot - a LOT - more MMU companies around than there used to be. Sampling can be a drag, but if you work out which ingredients are upsetting your skin, that can narrow it down quite a bit.
Definitely stay away from bismuth oxychloride, as that seems to be a major culprit for a lot of women, but most of the smaller MMU companies don't use it anyway. There are even mica-free foundations out there if that turns out to be the problem, though it's pretty rare.
Good luck!
ETA: You can spritz with hydrosol (the distillate left over from the making of essential oils, lavender is a good one for sensitive skin) both to get rid of cakiness in your make up and to keep your skin hydrated all day long - minerals don't run when they get wet. If you're on a tight budget, distilled water does the trick, too. And if you're massively reacting to something, only wash with distilled water mixed with a bit of ground oatmeal (the regular generic kind - don't cook it, just chop it in the blender a bit), and honey for a while - that'll usually calm your skin right down.