If you are new to selling online, you will probably be thinking about the process of getting the money from an online sale into your bank account as fast as possible and without paying too much in bank charges or payment gateway fees.
The easiest payment to set up is Paypal, easy because it’s as simple as creating an account and adding the email address to a payment configuration page on your website. WooCommerce and opencart make this process very simple indeed, as does any of the other proprietary eCommerce shopping cart systems. As to whether it’s the cheapest depends largely on how many products you are selling. A payment gateway such as Sage pay will charge a small monthly fee for their payment gateway services. It’s then up to you to talk to your merchant service provider (your bank) to sort out the cheapest fees for processing the money in to your bank account. The higher turnover your online business produces, the cheaper your costs are likely to be.
The only thing I can really say is, do your research and compare banks. There are great differences between the banks when it comes to merchant services charges. This is one reason why I do advocate using Paypal at least at the start. The charges, although not the cheapest are by no means the most expensive either.