If you travel I would get an Airline card for any airline you think you might fly. Even if you don;t use that card, you'll get basic entry level perk (e.g. for Delta's AMEX, you'll get free checked bag).
I'd also get a Citi Hilton Visa and a Chase Marriott Visa, get the min spends and you'll get 50-10k bonus points.
Also, get AMEX for Hilton and SPG and get the bonus points.
AMEX Plat often has a 100k point offer. If you see that get it, if you want this card (has a $400 or $450 annual fee, but you do get several perks, like $200 for an airline incidentals like meals, etc, Delta Skyclub access, Priority Pass for other airline lounges, etc).
Don;t need to get these all at once, but if you like "free" vacations this is one way to get them.
In past 2 years I've stayed at Phoenician in Scottsdale for a week twice, the Hilton Bentley in South Beach for a week over New Years (due to the dates this was a $1500/night room) for free. With free air travel as well.
I put "free" in quotes because I know I am substituting cash back for travel points, so it is not really free. If you don't want the "free" travel, but prefer cash back, I am sure others will chime in.