Really good question. To know it would be great as that is what one can visualize and focus stable attention on and thus receive much internal benefit from. I don't know the absolute best, and maybe there is not an absolute best, it could vary between stages. I definitely know that a good start is to use the image of the Sun to meditate on. Please do leave in the comments section what you think may be the best image for inner development to meditate on. End (5917).
Make the knowledge received, consciousness in action. Time for the consciousness is NOW. Decide now to act and change will follow. Consciousness shines in change, and consciousness finding itself is light. Light shining into darkness transforms darkness into light.