Depending on how tall of a blade you want, 1/8 - 1/4 in. will all work great. I like using 3/16 myself but you need to match thickness to intended use. For a maximum chopping power, you want probably 1/4" and tall. For more of stout bushcraft, 5/32 will work. For grinds, again, match the grind type to what it will be used for. I like a high saber grind for all around duties. The angle is acute enough to slice well and the spine is full thickness for batoning.
Cheers