As you have said, there are many Altcoin in circulation, but it is difficult to choose a potential investment Altcoin but if you have knowledge I think you will select some Altcoin in 2018 potential. Here are some Altcoin that I feel should invest: ETH, LTC, NEO.
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https://bitcointalk.org/index.php?topic=5036235.msg46083258#msg46083258