On sale this week at Target, 4×6 prints are on sale for $0.10 each. To get 50 prints FREE, you can use the $5 off 50 prints coupon from Shopkick, or the $5 off 50 4×6 prints Target coupon.
Alternatively, you could make two orders of 50 prints each, then use the Shopkick coupon for one purchase. Then purchase the second set of 50 prints with the Target coupon. Ultimately, if you work it out right, you could get 100 prints completely FREE!