•Will put your saving in this bitcoin? why or why not?
•Question is bitcoin gold comes from bitcoin?
Bitcoin gold or bitcoin cash or other useless currencies that use the name of bitcoin and created by a hardfork, are mainly genetically modified bitcoins. Their network difficulty is low and that's why few greedy miners are still mining these coins. But in long run these are not going to sustain.
Invest in bitcoin only. It is the pioneer in crypto currency world and immensely popular. If you really want to make good amount of money, invest in bitcoin. There are few altcoins like ETH, Neo, dash or litecoin are also there, but never consider BTG or BCH.
Wait, what?
These altcoins that you're talking about on your last sentence, aren't they are also a modified bitcoin? - http://whatis.techtarget.com/definition/altcoin
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As for the OP, BTG isn't a bad choice since it have a cheaper price as of the moment.
Also, there's a higher chances for profit on BTG than BCH because the latter have already a bigger marketcap. (it's less likely for a 2x, 3x etc)