If you do a lot of domestic travel one of the easiest things to sign up for and get is a Southwest Companion Pass. We’ve traveled *free/cheap for years using it.
https://creditcards.chase.com/a1/southwest/60KPlus - $2k min spend
https://creditcards.chase.com/a1/southwest/60kPremier - $2k min spend
Companion pass needs 110k miles in one year. These two cards combined give you 120k.
The good thing about companion pass is it makes travel BOGO free & you can use miles to pay for your tickets, the value of your miles double, all you pay for is taxes.
Free = Last year I used my $300 CSR travel credit on a southwest gift card, pays for my taxes.