A resource is helpful when it has many examples. Igbo has many twists and turns and so the more the examples, the better. If you give few examples, it is hard to capture the full complexity of Igbo.
Onyinye is a great tutor. She is very kind and patient but firm. I have ordered a lot of Igbo books from Amazon and even attended a brief in person group class, so I have tried various ways to learn Igbo. In one lesson with her, she blew me away!! Her materials are thorough and provide many examples.
This is the most comprehensive set of lessons I have come across so far.
Chidimma, San Francisco USA.