I don't know your skin, but what has helped me is the Clinique Anti-blemish solutions 3 step system. I know a lot of people hate the normal 3 step system as it's really harsh on the skin, but I find this one less harsh - and it has really helped my hormonal acne.
For flaking skin, I've used La Roche-Posay Cicaplast. It's not a product that should be used every day. But it heals the skin and it does it well. I've used it under makeup (similar to a primer) and then after cleansing at night as a night treatment, and it takes a day or two, and my skin looks fine again.
When I had hormonal acne, I used my normal foundation on the good bits of the skin, and then I used a full coverage foundation (as I simply can't get concealer to behave) on the bad bits. I set it with a light dusting of transparent powder.
You can have a look at this video - I found it very helpful: www.lisaeldridge.com/video/12764/acneblemish-covering-make-up/
I would go to a good makeup counter and ask for samples of foundations, and test the whole look at home to see if the coverage and colours of products are right for you.
You might have time to buy the products before the party if it works for you, or you might have enough product in the samples to do your makeup (and then you can buy later if you like the products).
I've never had powder as samples, so you might have to buy that without testing it first.
I personally like Laura Mercier Tinted Moisturiser (I use the oil-free one as I have oily skin), Diorskin Nude foundation (more coverage than the Laura Mercier TM) and the full coverage foundation I used as a concealer was Vichy Dermablend.
I really like Nars Translucent Crystal Light Reflecting Loose Setting Powder, but really, you can use any powder that you like. Mac Mineralize Skinfinish Natural is very nice too.