I have been juicing and drinking wheatgrass for years. I tried to grow it, and it's SO inexpensive and it grows so fast, but no matter what I tried, it would always get moldy so quickly.
I find the best way for me is to buy a flat of it at the store, but even that gets moldy fast. A dude at Whole Foods suggested I put it in the fridge, and that seems to keep it from molding, but watch how cold your settings are at, because if it gets that crunchy/frosted feeling at all, then it will all turn wilted+limp and gross
If you are going to make the effort to consume wheatgrass I would suggest you not take the dried up version, the pills, the powder or the pre-cut due to killing the living enzymes, they say it is best if you juice it and drink it within 10-15mins. If you're gna do it, you might well do it right.