Risky buy unless you know the seller and that they got it from a pharmacy. There's a ton of counterfeit Adderall out there, and it's always meth. Even the XR gelcaps are counterfeit now.
Meth isn't a terrible substitute, but it's not going to be dosed correctly or even the same dose pill to pill. It has a much longer half-life.
Ritalin is probably safer because it's less controlled in other countries, so it might be cheaper to import the real stuff than press fakes.
Purple Frog: