I didn't think you could get more than 270 publicity points in Chapter 1, without resorting to spending credits.

I decided to switch promotional campaigns at the end of Chapter 2. You can amass 210 publicity points in this chapter for a total of 480 points, so I needed to buy at least 320 points in Chapter 1 to get a total of 800 points. I spent 64,000 Gil to buy the 6,400 credits, which I lost at Sky slots, 25 credits at a time.