It depends on your goal. best resolution I suggest is 100 meters which is hard to achieve. but you can not use a network more than 900 meters distance. so 600*600 and 900*900 are the most common sampling network I suggest.

and... you can wait for your friends to answer. they may have a better suggestion.

Good luck Bro

I have a work on my profile on soil survey for land evaluation. meanwhile I will report further later