Temur Sabertooth + Gaea's Cradle + Kiora's Follower + Little Bear

How it works

Activate Gaea's Cradle by tapping it, adding at least six .
Activate Temur Sabertooth by paying , returning Little Bear to your hand.
Cast Little Bear by paying .
When Little Bear enters, it triggers itself, untapping Kiora's Follower.
Activate Kiora's Follower by tapping it, untapping Gaea's Cradle.
Repeat.
Once you have infinite green mana, you may activate Temur Sabertooth any number of times and recast any creatures castable with green mana any number of times, effectively "blinking" your green creatures any number of times.
You may also activate Kiora's Follower any number of times.

In which brackets is this combo allowed, per Spellbook's Powerful tier?

1–2 · Exhibition & Core

Spellbook classifies this as Powerful — not for these brackets.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.