The guide to effective chemical dependency (aka Junkies) playstyle
If you want to benefit from Junkies prefix, you need to suffer withdrawal symptoms. You suffer withdrawal symptoms when you're addicted and not under influence of your preferred substance. This means if you're addicted to psycho, you won't get bonus to Junkies if you're under Psycho.
The maximum value of Junkies buff is 50%, and it receives 10% per active withdrawal symptoms, so you need to pick up at least five substance dependencies that you don't intend to satisfy to play this build.
To get addicted, consume 5 units of your new withdrawal source shortly.
Since withdrawals make your character suffer penalties, and simultaneously you want those withdrawals, you need to these dependencies to be something you don't use in fight.
Therefore, for ranged combat I propose Alcohol, DaddyO, DayTripper, Fury, and Mentats. You are free to consume psycho, overdrive, calmex and buffout. SPECIAL suffers following penalties: -1, -2, 0, -3, -1, -1, -1
For melee I propose Alcohol, DaddyO, Day Tripper, Mentats and either MedX or Formula P. You would suffer 0, -1, 0, -3 (-5), -1, -1 (0), -1 (-3) to your SPECIAL. FormulaP is harder to get ahold of to get yourself addicted but these stats are not very critical for melee.
If you're after Berserkers gameplay, not Junkies, you'll need MedX and Psycho addiction to remain at no DR and be able to use some kind of low-level chest for Dense mod.