The best place to start is with the Foundation page:
Userguide will explain all you need to know, the foundation chart under check colours gives a decent guide to what foundation shades match your skin tone, and clicking each product will give you info on price, coverage, SPF etc.
I suggest you start off looking for a foundation that has satin finish (EA's FF is satin with full coverage). MAC has a full coverage foundation. The popular dewy finish these days tends to have lots of reflective particles that make the skin shine and look juicy/youthful, so you can give them a try but I'd stick to the satins. Matte's will tend to lodge in creases, highlighting wrinkles.
It's a tough question you've put forward, the only suggestion I can make is to try Jurlique Silk Dust, be it rose or lavender- both do the same job. It's not a powder, it's an absorbent dust that you very very lightly powder on top of your foundation, and it absorbs moisture/oil, leaving your foundation lasting much much longer.
A lot of ladies here in hot/humid parts of the country (QLD, WA) swear by this, as it really helps to set foundation. It doesn't settle in creases because it's so very finely milled- it's got rice/corn starch in it I think. Basically to use, you would dip your kabuki brush lightly into the powder, tap off excess, then very lightly and quickly roll the brush over the face. If you use too much, you'll end up looking like a ghost
A jar should last you a lifetime.
You can also purchase Jurlique from Strawberrynet, it's an aussie brand.
You could also try Bare Escentuals bareMinerals Mineral Veil, same deal, corn starch based- we only just got BE products in this year in oz.
Try Makeupalley for user reviews.