How to make the most acceptable way to pay by card?

Question

Unity

The bottom line is simple - the game is ready, the game has a store of all sorts of goodies, the user chooses what to buy and how much, and at the bottom there is a "buy for .... $" button, the question is what to do after the user clicked buy / pay?
In some games, I saw they transfer to some site, while in others I immediately pay with a card.
In general, how to do it in the most acceptable way, that is, so that the user does not need to poke three hundred times and run around the sites, well, it’s easier to integrate ...
And I want to note that the game is not aimed at one country / currency.