Altcoins are alternative cryptocurrencies such as Ethereum and Litecoin. If you don't know yet what altcoins are, I'd suggest staying away from them until you have read up on the matter.

Given that 0.5 BTC is no chump change, I'd recommend getting yourself a hardware wallet such as the Ledger Nano S or a Trezor.

Buy one of these wallets directly from their stores, not from any third party resellers or eBay:
https://trezor.io/
https://www.ledgerwallet.com/

For all intents and purposes, both are effectively equaly secure. Ledger is slightly cheaper. Availability may vary.

Read up on how to use a hardware wallet. Keep your wallet seed back up secure and offline. Remember that every transaction you make is irreversible. Maybe play around with small transactions before moving everything onto your hardware wallet.

Keep your money off exchanges. Stay away from cloud mining. Stay away from ICOs and alts until you really know what you're doing. Daytrading is a great way to both make and lose money. Remember that trying to get rich quick is a great way to get poor quick. Not losing money on scams and pseudo-investment is half the battle.