Some good cryptocurrency exchanges you can look at are:
Pluses (offers many #altcoins)
Pluses (easy transfer from cash to bitcoin and bitcoin to cash)
Minus (No facility to purchase alt coins).
Once you find your feet, start investing with small amounts while you learn the ropes.
Follow the news and listen to credible commentators to inform your own decisions about what and when to buy.
While the risk can be overstated, online exchanges have been hacked, so you should spread you investment over two or three exchanges.
If you feel you simply have too much to lose in any exchange, you need to transition to having your own wallet. Cyrptocurrency wallets can be desktop wallets or offline wallets. Having a desk top wallet is more secure than en exchange, making sure you have done all you can to protect your device from hackers (anti-virus software, VPN, etc). When you have built up some real capital online, you can back up your cryptocurrency and store it completely offline, which is 100 per cent safe (just don’t lose your trezor or ledger).
This is my opinion based on my research. I am not a financial adviser and always encourage people to do their own independent research before investing.