It all depends.
Hunter pressure, susbspecies you are hunting, early VS late season, etc, etc...
As Bighonker pointed out, he has found lots of decoys are needed--becuase I bet he is hunting lessors in TX--which like lots of decoys.
As for Giants that I hunt, in the early season, I will use 9 flocked Bigfoots. Later I will use all 3 dz, and in late season I'll use the "garage sale" spread of added 2 dz mag shells, and 3.5 dz Real Geese pros, and a few magnets added for movement to get the numbers up.
As for high pressure areas, well it seems quality is a must from my experience. A tip is use something completely different from what they are used to seeing--meaning if everybody is using Bigfoots, use silos or shells---change up the appearance. But conversely, in very low hunting pressure areas, a guy can use 2 dz shells and do well.
In my experince it is best to buy the good quality gear so it lasts many years VS cheap gear that last a season or 2. You will be $ ahead and have alot less frustration too.