Create signup form that creates user, sub site & collect payment

I want to setup a new multi-site install where I will have a signup page where they enter their name, email, site url & name, submit payment via authorize.net and have the site created upon submission & successful payment.

Only on price will be charged, no different membership levels or upgrades, just a 30 day trial period.

I have wpmedev membership & gravity forms developer license.

I have a custom signup form I made here:
https://evantageaz.com/default-template/msr/
but don’t know how to add a auth.net payment gateway.

I have a site that uses paid membership pro which I think will do this but you have to pay the 200 per year for the membership upgrade to get the extra plugin. I see they have a plugin that might work on git-hub but it hasn’t been up dated in some time. Right now after a payment is made we have to create the new site manually.

Wpmudev has the pro sites plugin which will almost do everything but they don’t have a auth.net gateway.

Wpmudev has Membership pro 2 which will accept payment via auth.net which I need but was wondering how I can use the signup form to create new sites. I don’t need to restrict access to any membership areas, just collect payment & create site.

What I was going to try next was try and use a gravity forms with teh user reg addon along with membership 2 pro and see if that does what I need.

Also Gravity Forms has the user registration addon for wordpress and a authorize.net add on to collect payment. Maybe those would work but not sure which would be easiest if at all possible.

I know this is a lot of info but maybe someone has some advice based on their experiences?

Thanks!!
-George