Acuity is the king of online scheduling. It is the system I use and 99% of my clients. It is available as a desktop website and they also have an app. Perfect. Price starts at $0 per month.
It is all you will need when booking 1.1 clients and even group sessions (workshops, classes)
Link tree - Creates Multiple URL On Instagram
Linktree is a free tool for optimising your Instagram traffic, whether you’re a blogger, an artist or run a content platform.
You’ll get one bio link to house all the content you’re driving followers to.
Thinkific is a software platform that enables entrepreneurs to create, market, sell, and deliver their own online courses. You can also integrate your mailing list and accept payments with Swipe.
Paypal is the worlds most trusted online payment system. I have been using Paypal for years without any issues. You can manually invoice and integrate paypal into your other systems like Acuity.