Put shaped poly in the mains, but smooth or "rough" poly in crosses.
Using natural gut as a cross is a waste of money.
Gosen OGSM is good as a cross (it is smooth, never breaks, just thins out), especially with shaped poly mains, but I would not use it in the mains as it loses elasticity too soon.
Smooth poly mains is nowhere near effective as shaped poly mains (such as 7-sided Dunlop Black Widow) in terms of ball bite/spin. Natural gut mains is better alternative to smooth poly mains.