They are not stars, as it happens. DoubleDown calls them crystals, and they have exactly one job.
Where to find your crystal count
Look at the top left of the screen, near the Lucky Orb logo. That number is how many crystals you are holding.
Crystals are awarded to you by opening Lucky Orbs. An Orb can contain 2 to 6 of them, along with its chip reward, 1 to 3 bingo balls and a Wonder Card pack.
So they come out of Orbs. And as you are about to see, they go straight back into Orbs.
What they do
A Lucky Orb is a prize container you earn while spinning the slots. When you earn one there is a waiting period before it unlocks and you can collect the prize inside.
Crystals skip that wait. Spend them and the Orb unlocks immediately, prize and all.
That is the whole feature. They are not a currency you can spend elsewhere, they do not buy chips, and there is no bonus for stockpiling them.
When to spend and when to wait
Since crystals only buy time, the decision is really about patience.
Spend them when waiting is inconvenient - you are near the end of a session, or you would rather not leave an Orb sitting unopened until tomorrow.
Save them when you are happy to let Orbs unlock on their own schedule. They will keep accumulating from the Orbs you open in the meantime, and there is no penalty for a large pile.
Either way, an Orb pays the same prize whether you waited for it or unlocked it early. Crystals change when you get it, never what you get.
One thing they do not do
Crystals do not improve what is inside an Orb. That is set by something else entirely: the amount you bet determines which kind of Orb you have a chance at, from Common through Rare, Superior and Epic up to Legendary.
And no crystal, Orb or booster changes what a slot spin does. These are random-number games with no memory and no pattern. Chips in DoubleDown are play money that never convert to cash or prizes, so the only thing being sped up here is your own fun.
Spend your crystals however you like. Then come spend a couple of minutes on https://www.ddpcshares.com/double_down_c ... tion_codes - where today's free chip codes are already posted.