You need to get yourself the pure shit. Search for JWH-018 on google, its the synthetic cannabinoid that is in spice. 1 gram is like 40 bucks, and the dose is 1-3mg. This shit is no joke, if you smoke too much you are going to be tripping balls, for A LONG TIME.
The best thing to do is buy a gram, dilute in 1 liter of ethanol so each millileter has 1mg of jwh in it, then apply it to any smokable material, let the alcohol evaporate and smoke it. It will probably be illegal soon though, just like all wonderful research chemicals, so stock up!