There are many good site where you can buy Bitcoin, Go to major Exchanges (the legit ones).
You can go to Coinbase, Coinmama or if you're in the Philippines you can install an android app (Coins.ph).
You can buy bitcoin as a whole or a fraction of it. Fraction of bitcoin for example (0.00000001) is called Satoshi.
When you got your (coins) transfer it to a Hardware wallet or a private wallet where you have your own Private Keys.
Secure your private keys and recovery seeds and be safe. If you bought a coin that is not supported by any private wallet or Hardware wallet, that's the only time you can store it on your favorite exchanges but be sure to enable the 2FA (Google Authenticator).