Like pps have mentioned - the first one
Walmart or something we might use during our trip and then PP. Uber, Starbucks (although I use Bing for Starbucks), Landry's (Y&Y at AK, TRex and RFC at DS).
I also like
Amazon because you can get other gift cards with it - I save them up in my Amazon account and then use them for Southwest cards.
edit - I do not get SW cards as my discounted one on SB because SW only allows 4 forms of payment per transaction. It is just easier to get Amazon and then use that to get a SW card of a bigger denomination (usually $200). I have done the - everyone separately/one way tickets and it is just a pain to check in.