After you collect at least 60 light seeds you don't need me to tell you that it is time to return to the temple to activate the first of four power plates.
A power plate is a colored disk that is embedded in walls around the levels and let you perform special jumps to get to another unreachable area in the level. The plate you pick unlocks a set of four levels in the world map. Each plate can be activated in any order so it is up to you.
Since you have been trusting me this far I would definitely recommend that you activate blue plate which is located on the far left. It is the most thought out and best implemented power and it is the most fun to use. So, if you get tired of this game and want to quit early, at least you know you did the best one first.
If you want more help on which power to pick and what each one does, check the power plate guide