Using a controller with my mobile Terraria changed my life. I cannot hyperbole it up enough for you. Love love love it. Love. And I even love it. To pieces. And back.
I'm on iOS like you and I use it mainly with my iPad. It's a MadCatz CTRLi and it is
not one of the supported controllers, however it works fine.
One thing to note for the iOS controllers - there's no way to specifically target using the cursor. If you're building or mining and you want to get
that specific block you'll need to still use the touch screen. The Android controllers are able to switch to that exact mode, but not iOS controllers.
I also can't bind items to the D-pad like I can on the Xbox 360. I'm not sure if that is a limitation of my particular controller, of iOS controllers in general, or all mobile controllers. But even without the target cursor and D-pad binding it is soooOOOooo much easier playing with the controller.
Here's what 505 Games says on their
Support page for controllers
The MOGA Hero Power and Logitech PowerShell controllers are recommended and supported by Terraria.
However, since we have adapted and optimized the control scheme for touch, controllers are not required to play Terraria on mobile devices!
I recommend making sure the controller will work with your device before purchasing by researching the supported devices, as well as buying from somewhere that will accept returns if it doesn't work out. Good luck!