I use them all...
With Shopkick you can earn 'kicks' directly to a DGC (or a number of different GCs) in 25$ or 50$ denomination. You can scan receipts for 'kicks', and you can also scan items in-store. So if you're mooching through Target, open up the app and see which items give kicks just for scanning-- no purchase required. Some stores have a 'walk in' bonus. So if you find yourself frequently walking by CVSes and/or Targets, you can earn points by opening the app in the store front. What I particularly like is that you set a goal in the app-- for me it's 6250 kicks for a 25$ DGC-- and with every scan, it shows me how close I am to that goal (see image). They also have a tab called 'Discover' where you can earn 1-3 kicks for watching short adverts. You don't have to
actually watch-- just hit play and in 30 seconds it'll be over.
Ibotta gives cash back for grocery purchases. Most stores you'll be able to scan receipts; some will insist that you add your loyalty card. You can also get cash back on online purchases à la Rakuten. With Ibotta you need to add the items to your 'list' before scanning the receipt, or else they won't count (or shopping in-store). You can cash out when you reach 20$ balance. They'll Paypal you money, or you can get a GC.
Fetch is a sort of counterpart to Ibotta, in that you don't have to add items to a list before scanning the receipt-- the app will read your receipt and reward you with points. You can use the points on gift cards (no DGC though). Most GCs there start at 5000 points (5$ value) though some are 3000 points (3$ value). It can be easy to rack up points there if you frequently buy their partner brands. There are also bonuses periodically.
Rakuten gives you cash back on online purchases. I have a browser extension (on Chrome) and I can just click to add the cash back before I make the transaction. You can also go to Rakuten's website and navigate to the merchant from there. They've also got an e-gift card shop (again, no DGC). If we feel like takeout, I'll usually check there first to buy a gift card, and then we'll order. There is also the possibility of in-store cash back with Rakuten if you register your credit card on the site, and add the in-store offers. So when you make a purchase with that registered card in the store, you'll get credit. They pay out quarterly, though, so plan for that. Their default is to post a check, but you can get the money via Paypal too.
Receipt Hog probably isn't worth it, tbh. You scan receipts for 'coins' which can be redeemed for cash (via Paypal) or
Amazon vouchers or a VGC. 1000 coins will earn you 5$ in the denomination of choice. There are no specific partner brands, so you earn slowly. Also they push for you to register your email so they can credit you for online purchases. But that means the app gets to read your emails, which makes me uncomfortable but to each their own.
If you buy a lot of Blu-rays, or see Disney films in cinemas often, Disney Movie Insiders is a decent bet. 1000 points will get you a 10$ DGC; 2250 will get you a 25$ DGC. But it's also fairly slow going. A cinema ticket will earn you 100-150 points; purchasing a film on
Disney+ premier access is 300 points. There's also a thread elsewhere on the Budget Board which posts bonus codes which adds 10-25 points per code. You can link Regal and Fandango accounts to DMI, so if you make purchases there, you'll get the credit in DMI without having to do anything. Like I say, if you purchase every new Disney release, definitely get it. If not, you can give it a miss.