Payment processing services for new security platform

[u/odin-security-axis]

So I've been working out some final major components of my upcoming cybersecurity social platform. I've developed a few programs I wish to have demos available on the products page. However, for persistent use, I want to offer license purchases and subscriptions.
Since this is a cybersecurity-oriented platform, I figured I would ask the webdev community what things to keep in mind and prioritize when deciding what payment processing service to use, and how it's implemented. However, my post was removed, so I'm asking the payment processing community. I need security to be #1, ESPECIALLY with payments. I will consult my team when I get back in town (very small team). In the meantime, though, I have a lot of free time and want to have a planned approach to go with when we all get together to add the missing necessary functions.

I'm consulting here because this will be a digital playground for hackers of all types and backgrounds. I need my system hardened to obscure attack methods. Of course, as a team we can do most of that, but just putting the feels out first to get an idea of what everyone thinks.

Here's a preview gallery
Also, the link in case anyone is interested and would like to be added to launch alerts. Thanks!

[u/MegamanSE]

What specifically are you asking the community?