Could you be a bit more precise then 'synthetics' because at the moment we are looking at a few different drug familys comprising of hundreds of substances.
You're going to have to do your own research and come back with harm reduction related questions concerning the drug(s) you've come up with; we'll be happy to help you with dosage, combination concerns, side effect mitigation and other topics to help you use once you've made the decision to use a specific drug or drugs.