HI, as the single mother or a 3 1/2 yr old that no longer wears diapers,who did not get any help from anyone(no WIC,Government,etc). I used to look every where for the best prices. First I agree with the previous suggestion of signing up for all the online baby clubs and supermarket clubs. I have gotten and still get very good coupons. The other thing is sign in for Enfamil coupons by logging into their web site. They used to send me checks for 8,6,5,3,2,1 dollars off. And those are good if you are on a bind and need to buy your formula last minute in a Pharmacy or supermarket. In general try to avoid these places. I prefered to buy in bulk at any wholesaler for example : COSTCO,Sam's Club or BJ's would have the formula,diapers and wipes cheaper , I know the membership can be hard but see if you can split it with someone, In general these places have bigger cans/boxes for less. The next place that has great deals on these things when they are on sale is Target. Maybe once a month the formula is put on sale and if you get the checks,that is a good place to use them. Diapers also are great from there since many times if you buy 2 packs the give you a $5.00 gift card. CVS has great deals on diapers,and if don't mind using their brand,you can get great deals.
Last but not list I do not know if there is a store called Building 19 in your area,but here in Mass,there are many. The have great buys on wipes,and diapers sometimes.
Hope this helps