It totally depends on what you're really looking to get out of your recordings. For demos, quick and cheerful unprocessed tracks I'd probably just stick with a line-in (some of the amp sims such as Amplitube aren't terrible) and use GB's stock midi drum kit. If you've got a small mixer you could also stick in a mic to the same line in and, as long as you seriously boost the gain and gate it slightly, vocal tracking is also possible.
If you're really looking to get marketable and radio worthy recordings, I would properly invest. My home rig is pretty simple at the moment, Scarlet 6i6, Avantone CK6 and Samson C01 and a reamp box. However, couple that with a decent DAW like Sonar (even Reaper would do for a beginner) and you'll be able to get some nice sounds.
My experience of ipad recording was frustrating. Not enough screen room and good software for my limiters, EQ, mastering... the list goes on. Unless you have decent preamps too, you'll be struggling to get anything really listenable.