DocsGas Drip
You pay your own gas; Astro makes sure you never run out.
Every transaction you send on Astro (placing a bet, approving the Bankroll, withdrawing) costs gas in ETH, and you pay it, like on any other chain. Astro does not sponsor or subsidize transactions.
What Astro does automatically is keep your wallet from ever running dry: if your embedded wallet's ETH balance runs low, Astro tops it up (a "drip") right when you need it, before login, before a transaction, or after one fails for lack of gas, so you never have to go buy ETH yourself and bridge it in just to keep playing.
That top-up isn't free money: its cost is deducted from your own USDG balance at the time of the drip. It's prepaid gas, delivered automatically, not a subsidy.
If you're on an external wallet rather than the embedded one, you're responsible for keeping it funded with ETH yourself, the same as on any other dApp.