You can basically put the potential problems into 2 categories: Financial Losses and Freedom Losses.
For financial losses your 1st risk is a bad seller, if things go wrong you will need the escrow system to get your money back. If you are a noob this might take time while you build your reputation and extend settlement time. Otherwise there isn't much risk here.
For losses of your freedom it depends how bad your jurisdiction is but there really aren't many places left on earth where you will be abducted for a small amount of cannabis. Again if you stay with proven sellers the stealth will more than cover this possibility.