This is not a strictly straightforward subject, but the font of all knowledge is this site: https://headforpoints.com

In essence, it depends a lot on what you want to spend points on, and you'll spend on the card to generate said points.

There are some better Mastercards coming to market at the moment, but all depends on your circumstances. I'd definitely recommend reading the above website, it's a fantastic resource. (We've done 10+ long haul flights in First on points so it does work well if you're circumstances are a good fit for racking up the points and vouchers).