There's no way to claim BTG at this time because there is no live BTG network. The only thing that happened was the UTXO snapshot that will become the UTXO set if/when the coin is actually launched. As it stands, the developers haven't been able to properly add replay protection, and everyone is waiting around. Once the network is launched, assuming there is replay protection, you can move your BTC to a new address and then import the original BTC address(es) into a BTG wallet.

It's really odd that so many exchanges launched trading for a coin that doesn't even exist yet. What happens if the Bitcoin Gold developers never even launch it? It seems legally precarious to allow people to buy imaginary coins.