I never did the 1e version but overflow just states that at finishing your element is no longer gathered, if you had any stance impulses they would end (part of the gather description), and that you can only do 1 overflow per turn

you can start with either 1 or 2 elements, and at 5th and every 4 past that (9/13/17) you can strengthen your current elements or add a new 1. at level 17 would give access to them all

Ill put down the progression table, dont feel like thats being unfair to Paizo to show