Ceumannan, a Gaelic language course produced by Stòrlann Nàiseanta na Gàidhlig, is a great resource and one that I use for my Gaelic tutoring. You can buy paper textbooks The Gaelic Books Council, or download PDFs from the Ceumannan website.
The organization is as follows: Each book is divided into Modals, which are subdivided into Aonads (Units). At the end of the book is the Cànan section, which provides additional exercises. Also at the back of the book is Faclair Mòr, which is a glossary of vocabulary. Faclair Mòr is also available as an app - at least for iOS.
……Àireamh 1, 2, 3, 4, …
……Sùil air ais 1, 2, 3, 4, …
….Eacarsaich 1, 2, 3, 4, …
The audio program is available via soundcloud.com. The organization mirrors that of the book, but the tracks are sequentially numbered. Be sure to get the audio program key that I've made to correlate the track names to the listening extracts in the book. There is one per book.
There are 5 volumes of Ceumannan:
Ceumannan 2 (Guide coming soon)
Ceumannan 3 (Guide coming soon)
Ceumannan 4 (Guide coming soon)
Ceumannan 5 (Guide coming soon)