i just trade altcoin and for me poloniex, bittrex, c-cex, yobit is the best place to trading altcoin.
now im trade at c-cex and buying some $fch (fastcash) at 2500sat, hope price back to 7000sat
Till now I didn't tried anywhere for altcoins but I tried to sell bitcoins in localbitcoins and kraken both are good place sell or buy the bitcoins. As of now we can hold the bitcoin and we can sell it in this year end.
i think it depend on time and situation, in different time you have to thing differently and to select different places of investment, for example some time you will be thinking to invest in gambling when you are in gambling mode and some time to give preference to alt coins where you can also make good profit. so it is not fixed to invest only on place,