Amphetamine tolerance can be slowed through daily administration of magnesium supplements and co-administration of NMDA receptor antagonists. Magnesium supplements are found in different forms; the cheapest is magnesium oxide. It's generally what you're going to be buying at drug stores, supermarket pharmacies, GNCs etc. Magnesium oxide has a very low bioavalability compared to magnesium chloride, lactate, and aspartate so these should be used instead if at all possible. Oftentimes you'll have to order the useful forms online if you want them as they're hard to find in person.
Besides magnesium, the most accessible NDMA antagonist used for amphetamine tolerance management is dextromethorphan. Long-acting preparations like delsym are popular for this purpose as they reduce the need to re-dosing parallel to any stimulant re-dosage. As with all drug mixing, it's important to proceed with caution to avoid dangerous interactions. DXM and amphetamine both increase blood pressure and in rare cases combining them can cause serotonin syndrome.
Take care of yourself! It's very easy to neglect the body for days on end during a binge, the time it needs nutrients most. Even if you don't feel like it, try to eat and drink. A good idea is to wash the initial dose down with a large glass of water and then keep drinking during/ after you use stims. Eat a light snack a few hours earlier if you plan on a binge and try to choke down some high-protein foods when you can. Malnutrition is serious shit that no one ought to deal with. The same goes for sleeping; two or three days is probably the longest you should binge. Sleep deprivation is bad for you and the high gets progressively shittier as you go on. Even a few hours of rest during heavy binges can do a lot of good for your body.