Aid Foundation and skin care?

I use Clinique Superfit Foundation that I used to love, but for some reason its started to settle in my (wide open) pores and do as the white dots on my face. I have not changed my skincare routine, so I do not whats happened. I have oily skin and cleanse, tone and moisturize twice a day with the right products for my skin type and exfoliate once a week.

do I need to use moisturizer before I apply my foundation?

This morning, I applied moisturizer on my face and let dry about 20 minutes. I put on a little foundation and brushed some sun on it. However, when the afternoon came my skin was terrible and seemed really oily, which felt really uncomfortable because it was very hot today. Does anyone have tips to keep my makeup looking fresh as what it looks like the morning when I come to apply it. Thank you!

How to lighten my foundation?

So I bought Revlon ColorStay foundation a few days ago, and when I opened it to try it, it was too dark for me. I tried to return, but they wouldnt take it back because I had already opened. . . Is there anyway to lighten my foundation? Because I love Revlon ColorStay, and I do not want to buy a new bottle of it and I am a student on a budget! Should I mix it with a moisturizer?