The penalties for possession and shoplifting vary by state, but are usually fines (which also vary by state, but you're looking at, at least, several hundred dollars). Your problem is, you are now facing both charges (since you did not complete your diversion program), which might even include some incarceration. (Usually depending on how busy your jurisdiction is, since judges usually have some leeway.)
If you don't have a full-time job, you may qualify for a public defender. Can't hurt to ask. It's worth retaining one, though, even if you have to beg or borrow to do it. Conviction of a drug charge will disqualify you for student loans, and could even get you expelled.
There's no way you're keeping this off your record. (A diversion program doesn't make your record vanish, anyway, it only results in the outcome of case being recorded as "dismissed.") You may qualify to have your record "sealed" or "expunged," in some states, sometime in the future.