No mining Bitcoin Gold is not live yet. But it looks like it will be available soon !
The test net has been started yesterday and miners/pool operators are testing the waters right now on them.
You can surely join one of these testnet pools BUT keep in mind that all the coins that you mine in the test net have totally no value even after the main network and the official wallets are introduced. This is just a heads up in order to understand that you can't expect anything out of it.
Regarding how to start to mine, since BTG is equihash, you can use something like EWBF cuda zcash miner. Just point the pools and you should be fine. Look up the forum for the thread.
Anybody knows is there a deadline of Mainnet start? Any countdown timer or so on? I think it will be very profitable in the first hours after starting but I can't find when will it be happen
They haven't declared a final date or something for when the mainnet will go live.
It has wasted us many time.
You practically didn't waste anything since the coin is given away for free anyway.