I have a group of 3 completely-new-to-Shadowrun players I GM for, and this question came up straight out of the gate during Character Creation. I kept it simple, and House-Ruled that spending Karma on Attributes, Skills, Contacts and Nuyen was the last step in the Creation process. I view it as the stat points you gain from the Priority Table establish your character's raw Baseline of Ability, or Inherent Potential. Spending Karma is a conscious act of focusing on specific portions of the character for improvement. I feel this leads better into Spending Karma during Gameplay, with a consistent conceptual model of how Karma works.