If you're looking to trade many smaller cryptocurrencies and altcoins, use Digital Surge or Swyftx (see my Digital Surge review and Swyftx review). Digital Surge and Swyftx both have over 200 cryptocurrencies available to trade, far more than other exchanges (with the exception of CoinSpot which will rip you off with 1% fees for most cryptocurrencies). These are not "exchanges" per-say, but rather "brokers" where when you place an order to buy some obscure cryptocurrency, they will send your order to one of the many market places they have access to and fill your order for you. This is unlike normal exchanges where you're trading directly with other users of the platform (e.g., with Bitaroo, when you buy bitcoin you're purchasing Bitcoin from another Bitaroo user selling it -- with Digital Surge or Swyftx, you're not necessarily trading with other Digital Surge or Swyftx users). This allows Digital Surge and Swyftx to accommodate decent trading volume even for tiny cryptocurrencies.