There are many websites where you can buy bitcoin so I picked the ones I like most to share with you. You can either buy bitcoin from other people on a marketplace or directly from a merchant. For the beginning it might be easier to chose a merchant over a marketplace in order to get used to bitcoin transfers.
The two marketplaces I prefer are Paxful and Localbitcoins.
Localbitcoins is a Website that offers you the opportunity to buy and sell bitcoin locally. Unfortunately I couldn't try this service myself because it is not available where I live. But it seems to be a really cool concept.
Please keep in mind that the use of these sites isn't completely risk free as there are also scammers.
Before I discovered Paxful I used anycoindirect to purchase bitcoin. It is a very convenient way to buy your first bitcoin as it really isn't difficult. They also sell many other cryptocurrencies like Etherum. But the website is only for users from Europe.
Coinbase works very similar to anycoindirect. You can buy bitcoin and many other cryptocurrencies via bank transfer and credit card. You can also earn free cryptocurrencies on Coinbase by learning about them.
So Coinbase is a nice place to start your bitcoin journey.
Please keep in mind that bitcoin is a cryptocurrency which has a high volatility and might not be suited for everyone.