All of them. As many times as you can.
People frequently ask me which credit card they should get (and every time I die a little on the inside because I don’t have any affiliate links to make money off of them). But it’s a question that I find challenging to answer because I don’t think that there’s a single credit card that people should get–people should get them all. The best credit card strategy is to apply for new cards as quickly as you can meet the minimum spend requirements on your previous cards so you’re constantly earning sign-up bonuses. Sign-up bonuses are currently the single best way to earn points in the current environment.
For example, the Chase Sapphire Preferred–which seems to be the gateway travel credit card for many people–currently offers 40k points after spending $4k within the first three months of having the card. This isn’t even the best the offer has been (it can go up to 50k points, ignoring the 5k points you can get for adding an authorized user). But that means that for the first $4k you’re spending on the credit card, you’re essentially earning at least 11 points per dollar spent. Or the Citi AA card which offers 50k miles after $3k in spending. That first $3k spent is earning over 17 miles per dollar. You’re not going to get anywhere close to those numbers on ongoing everyday spend.
In addition, by applying to credit cards as quickly as possible, you’re also resetting your clock on when you can then churn those cards. Chase cards are churnable 24 months after receiving the sign-up bonus, so applying for and meeting the spend earlier means that you have to wait less time to earn the bonus again in the future. Granted, there are some banks that are cracking down on this, but this game always evolves, so you should take advantage of opportunities as they arise.
Now, I’m a bit of a hypocrite because I’m not really following my own advice: I haven’t been applying for as many new cards as I could be, but this is mostly driven by the fact that I’m sitting on more miles than I can redeem so I haven’t been too focused on earning. But I’ve accumulated many of those miles from applying for (and subsequently closing) lots and lots of credit cards.