Testin on real devices with real builds are essential but it´s also very expensive.
We have just started to build our test central and it is already becoming a money eating machine. So if you can use friends and family, then it would be the best way.
We have multiple devices of all sorts, the worst and most expensive is the iOS stuff. We recently had a huge problem where our iPad Air and iPhone 5 and 6 worked perfect, while the testing group at Apple denied the app, due to that it got messed up on the new iPad Air2.
So now we need to grab ourselves another iPad just to test our apps on it.
Apple is also the worst in every ways as you need to add the hardwares number to your developer account for the app to be able to run on it before it is released.
The second most stoopid thing about iOS apps is that there is no way to test the "real" build. You can only test the AdHoc builds and you need to submit the Release builds. So it´s a bit scary to submit an app to Apple every single time. Also having to wait 5-7 days before apple gets off their ..... and test it and replies makes it even worse.
You also need one hardware running OS X in order to submit the app to the appstore. So if you dont own a MAC you pretty much do not wanna get into iOS apps anyway.