First of all make yourself sure you keep your BTC properly, dont use online wallets for that. Use Ladger Nano or Trazor as HeRetik said, if case you dont want to buy hardware wallet run Bitcoin Core on offline computer, connect it to internet in only case you want to make a transaction.
   You can trade your coins on Bittrex or Polonex, you can buy not only different currencyes but also tokens, some token prices behave differently compare to BTC price, so you can make profit this way.
   But actually our motto is HODL, it means keeping BTC forever