Start at air.
Elements you start with: Fire, Light, Water, Time.
G1: You use Water and Time. You decide to go through time.
G2: You can use Fire, Light, Aether. You use aether.
G3: You can use Fire, Light, Darkness, Death.
You can use a mono at any point. If you use a mono with elements remaining (IE, if you don't use all your currently available elements), you cannot push through anything.
So let's say you start at air:
Elements you start with: Fire, Light, Water, Time.
G1: You use water and time. You push through time to aether.
G2: You can use Fire, Light, Aether. You use none of them and use a mono.
G3: You can use Fire, Light Aether.
Another air example:
Elements you start with: Fire, Light, Water, Time.
G1: You use water and time. You push through time.
G2: You can use Fire, Light, Aether. You use Fire, Light, Aether. You push through water.
G3: You can use earth and life.