To start off I'd actually recommend investing in some altcoins, such as NEO, Monero, IOTA, and Verge. You'll see a much larger return on investment using altcoins, whereas BTC price has approximately peaked until there are some upgrades to the network.
You can register for an account on an exchange such as cryptopia, bittrex, or bitfenix once registrations reopen, however prior to this you'll need to get some bitcoin to trade against, you can buy bitcoin for fiat currency using
www.localbitcoins.com