I heard the hardware wallet Ledger nano does support BTG. So if I buy a ledger nano would I be able to claim my BTG on there?
No. You would only be able to store BTG there. But not claim your BTG from your old wallet because there is no import option in Ledger Nano S.
You would need to import your private key in a BTG compatible wallet and then send your Bitcoin Gold to your Ledger Nano S wallet.
You can see which wallets suport BTG in their website:
https://bitcoingold.org/