Welcome to Bluelight
Recommending drug combos is generally frowned upon, this site focuses on HR and recommending polydrug use is antithetical to that.
Now that my obligatory mod duties have been satisfied...
Personally I think that if you want the most from amphetamine you should take it on its own. Find an engaging activity that is productive or fun and go to town, then when you are at the tail end use an opiate or benzo to have a nice chill comedown.
If you do end up mixing opiates, benzodiazepines, and amphetamine/stims all at once please don't make the mistake of thinking you can handle more opiates and benzos. The stimulant can disguise a potentially lethal OD of CNS depressants and if the stim wears off before the depressants do it can put you in a dangerous scenario.
I know from experience that benzos can make you think you are a lot less fucked up than you actually are, so just be careful with your doses.
Stay safe