Here's WizardCrab with more info:
"Craving something new at champ select? Get fed on these limited time bundles. They’re flexible in cost, meaning the final bundle price will automatically adjust to reflect only what’s new to your collection.
All-in Bundle – 50% off at 2210 RP (4507 RP if you need the champions)
Blow up the Rift and one-shot your foes with this face-melting bundle of explosive terrors. Will you go ham or go home?
Fierce Feral Flarers Bundle — 50% off at 2437 RP (3825 RP if you need the champions)
Unleash your barbaric instincts and emerge from the fog of war an untamable beast with this brutal bundle of Feral Flare junglers!
Metal > Flesh Bundle – 50% off at 3000 RP (5010 RP if you need the champions)
Get ready to lead the march of machines in metallic style! With all the updates we’re making to bots, it’s about time our automaton friends got an artificially intelligent bundle to call their own.
Unlock these bundles before the sale ends on May 7th at 11:59 PM PST!"
To help you choose, here's a set of skin spotlights for each bundle!
Fierce Feral Flarers Bundle:
Metal > Flesh Bundle: