For now your phone will be a great way to capture your ideas (I use mine everyday), but when it comes time to produce a decent recording of your ideas, an interface is critical and digital audio workstation (DAW) are critical.

The DAW software Joseph mentioned is a great place to get started. As far as equipment goes, there are really great companies that are putting out high quality equipment at really reasonable prices. I just picked up a Focusrite Scarlett interface and it is working out awesome! Check out this package when you're ready - it has everything you need to get started!

http://www.sweetwater.com/store/detail/ScarlettStu?utm_source=Google&utm_medium=PPC&utm_campaign=none&device=c&network=g&matchtype=&gclid=CM_ygqXltbgCFQeCQgod_EAAmw

Have fun!