The Public Beta Environment is Riot's test realm, and it is a completely different product from everything else on this site. There is no essence to bank and no ladder to climb — a PBE account arrives with the entire champion roster and the entire skin catalogue already unlocked, because that is how the test realm works. You are buying access, not progress.
People buy PBE for three reasons: to try a skin before spending money on it, to play champions and reworks weeks before they hit live, and to test builds in an environment where losing costs nothing. It runs alongside your live account rather than replacing it, and nothing you do on PBE touches your real rank. Expect the test realm to be unstable — that is the point of it.
Note — PBE accounts ship with every champion and skin available on the test realm.