What's your favourite gear ratio?

Hi guys. I'm running as it came out the box; 42:16. As a real novice, perhaps I can ask your advice? I want more speed on the flats. I don't mind making it a little harder on the inclines which I suppose I have to have if I want the extra speed. Is my first step to reduce the 16 or increase the 42?

cheaper to change the 16T down but much bigger jump in gearing than changing the ring

have look at Gear Inch calculator to see the impact