Growing in faith isn’t found in super complex methods. Like Daniel learns from Mr. Miyagi in "The Karate Kid," it’s the basics that help you grow.
Paul is wanting to protect the Colossians from chasing the next "new" thing. Instead, he wants them to be founded in their faith and to walk in him.
God desires that we are rooted so deeply in our faith that, when the winds of change come, we won’t be shaken because we are firmly planted.