There are a couple of options available to you, dependent on your region.
A great place to start is to check if you are eligible to use Shopify Payments. Have you considered checking it out yet? There is a list of regions here at this link, which supports using our payment gateway. Shopify's payments gives customers a great checkout experience and offers them the ability to pay by credit card, use Google and Apple Pay, and also once enabled you don't pay any transaction fees which will save you money!
That said, if you are ineligible to use Shopify payments due to your location, you can always use a Third-Party Payment Provider instead. If you wanted to have a look, you can check out this page here, select the country you are located in, and then you will be provided with payment providers available in that country. In most cases with third-party payment providers, you will need to first create an external account with them in order to be able to use their services. Once you have an account set up, you can then follow our help doc: Configuring third - party payment providers.
I also wanted to mention, I was really impressed by your store and the work you have put into your wonderful blogs. Well done on that! As you are looking to add a payment gateway, what type of products or services are you hoping to sell? I would love to hear more and help you out with some business growth ideas. Have a great day.
Maz | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog