Building a Augemented Reality App requires a few things.
First, a computer to develop on
This can be a mac or windows laptop or desktop.
Second, a recent iPhone, iPad, Android phone or tablet (2017+)
The reason it needs to be recent is that some of the enabling technologies are only available in recent models. For example an A9 or A10 processor on iPhone/iPad, and iOS 11.
The camera and CPU detects what is in the real world, for example what is the ground, or wall, which is needed to figure out how digital items should interact with real objects.
You need software to help you design your App (your portal, balls, or drones for example), and instruct these digital items on what to do. Most AR apps for iOS are built with either
You can also reference many open source projects as a template to get started. Here's a curated list of open source AR projects
One of the best ways to learn about developing AR apps is to take an online video course. Many are available on udemy and coursera, usually for $10 to $15 for a full course. Check out: