It's relatively straight forward. Start with the Marquis, if you get a proper purple/black reaction with that then there isn't much the mecke and mandelin will do. If you are trying to identify a chemical other than MDMA they will be invaluable, but for just testing ecstasy it is a bit of overkill.
The mecke was mainly used for identifying DXM, which is hardly ever found in ecstasy anymore. It's basically obsolete now-a-days, although it is extremely helpful for testing psychedelics apart.. especially when used with the marquis. The mandelin's main use would be for identifying dissociatives like ketamine, although it's gained popularity lately because it can test for PMxx. That is also a relatively rare chemical, although one that can be very deadly so you can never be too careful to test for that. Both the mecke and mandelin are not reliable for testing MDMA on their own however, the mecke is much too sensitive to MDMA (it would cover the reaction of any adulterants) and the mecke simply isn't reliable enough to make positive identifications on it's own.
The marquis is a very trustworthy reagent, however. Carefully observe the reaction (especially the first few seconds) for any colors other than purple, blue or black. This may signify that it is MDMA cut with another substance, the marquis is probably the best reagent for showing multiple reactions in one sample. Once you have a positive Marquis, you can use the mandelin and mecke to make sure you didn't miss anything. Then you use the Simons to test whether it is MDA or MDMA, although if you get MDA it will probably be sold as MDA so that's not a huge issue either.
If you're just testing MDMA the marquis is really the only thing you need to be worried about. The other tests are helpful, but without a marquis they won't be conclusive.
be sure to take pictures or a video of the reaction if possible, that way if there is any question you can just post it in the Pill Testing Q&A section and get direct feedback
