Well.. if you are ever going to work on an iOS application, you are going to have to use XCode at some point. Sadly Apple decided that it would be best to limit the compilation of iOS applications to only be possible on a Mac machine so that would be the first thing you would need to have.

After spending a significant amount on the relevant hardware you will need to buy yourself an Apple Developer License (Currently $100 a year) and then buy an iOS device to test on (Cost quickly mounting up..). Ok now you need to start programming your applications, so download XCode from the App Store, login using your shiny new developer account and create a project. Oh and you’re going to have to learn Objective-C.
OR

Instead of learning Objective-C and saving yourself months of heart-ache (Though really you should learn it if you want to be making any sort of app, incase you need to make your own plugin’s) you could boot up Unity with your iOS license, create project and hit build-and-run (after setting up the application ID, creating a provisioning profile for the application and registered the devices to that profile..).

If your device is connected, the project will compile from Unity into an XCode project, then compile from XCode into an application which (if your device is connected) launch straight onto the device you’ve registered. Now that the application is on the device, you are free to disconnect it from the machine and the application will still be there! Congratulations you’re now an App developer. Now what if you wanted to put that same application onto 10 other devices, then what if you had to update them with a new build?

Well you could manually attach the device to the Mac, build and then push it to the device for each individual phone.. or you can do something called an Ad-hoc distribution. Welcome to your new best friend TestFlight.