If you are new to Drugstore shopping, I suggest you begin with one, I started with Rite Aid but then switched to CVS, until you are comfortable. You can always add another to continue building your stockpile later. Honestly, I have never even entered Walgreens to do my couponing yet!
Mastering Rite Aid
This is a great blogpost if you are feeling overwhelmed with couponing:
When saving doesn't pay
If you want to get more explanation for RedBox codes, try this: