Ingot Chewer and Mulldrifter can be cast cheaper when evoked, and then instead of paying the full whack, you can just make Offspring to keep one and get an extra EtB for value
As such the only time I have seen the -1 used is when you are digging for a specific card / answer or you have just made her onto a board she has no hope of surviving
Then you may return a creature or land card from your graveyard to your hand
Aang's got a lot to learn before he's ready to save anyone, so start at the beginning and journey with the Gaang to master the elements and save the world
The Hakbal EDH precon introduced some pretty powerful ones, like Ripples of Potential and Wave Goodbye, but there are also counter aplifiers like Hardened Scales you should consider
I hope you have a spectacular prerelease and pull a lot of good galaxy foil cards, but above all else, have fun