New to couponing

I just had my first 2 orders with walgreens. I'm trying couponing to stock up on items to help low income families and homeless. My 2nd order I got for 18 cents out of pocket, but seems like these "free" deals are rare with walgreens. How does one get started couponing? Like full on, planning and taking coupons to a store. Indont mind getting rebates for extra cash, but I want my total at register to be low without rebates. Thanks!