My iPad won't record anything from the input. I plugged in a mic that has a 1/8 inch plug but it doesn't register in garage band. I also tried a mic with a 1/4 inch plug with a 1/8 adapter and that didn't work either. Do I need irig even to use a mic with GarageBand?
That's not an input, it's the headphone jack.
The input it the third (extra) ring on the headphone jack - and you need a special plug to connect to that. Hooking a mic or guitar directly into the jack as you have been could damage them.
So go for the iRig, the Peavey AmpKit Link (which is probably better engineered) or run a USB audio interface into the camera connector.