I'm chinese too... pretty fair. I use the original formulation as I'm not that keen on heavy coverage! SN makes me look better than natural but still natural. Actually, most people just comment I look very rested and glowing with health. Which suits me just fine.
I agree with Jen. If you've ordered buttery and warm gold then just work with them. Ebony adds a touch of pink... and the only reason why I'm alternating warm and buttery is because I have bags of both that I want to use up. My preference is really Warm Gold even though with my mixture, you can't really tell that much of a difference.
I'd say... Try Jen's suggestion of 1 Buttery to 6 scoops of Ivory then add Ivory to lighten til you get the shade you want. Be sure to shake really really well. You don't want clumps of buttery on your face... from experience... it looks real weird!

you may wanna consider getting some ebony to add a slight flush to the foundation too... if you're like me, I hate looking too yellow. I'm chinese but defnitely not YELLOW! *gets off rant box*