If you are trying to meet minimum spend on say a Chase Ink card, you can earn Staples rewards points, plus 5x ultimate rewards points on a $40 purchase, and get $50 in iTunes value.
As Matt pointed out, this is not MS! Buying FAR items is MS. In addition, you do not earn 5% rewards on gift card purchases -- if we earned 5% rewards and were able to reach Plus / Premier status, then there wouldn't be a need to buy FAR stuff.
15% code is online only, and it's OOS online.
Using coupon codes to buy gift cards is a sure way to get infamously blacklisted from staples. They track IP address, CC information, mailing address, name. If you're lucky enough to get a gift card with a coupon code, this may be a one time thing. But be warned that you will be on their radar.
There are plenty of deals for money makers every week (granted, their deals have sucked the last few weeks - we will not be seeing any FAR paper deals anytime soon). But the past few weeks, you could buy 2 of the 5-ream case for $4 after coupon / rebates and use the $10 off $50 coupon for a slight $2 MM. The $10/50 coupon is "magic" (the $50 spend requirement is before coupons). Last couple of weeks, and this week, you can buy 2 of the 5-ream cases for ~$33 (including taxes) and get a $34 rebate.
On SD forums, many have reports their orders do not show up. It's most likely that the orders are manually reviewed.
Google "Staples blacklist" -- if you're blacklisted, you will only be able to shop at B&M stores only. No more ordering stuff online or the store kiosk.