Stellar lumens (XLM) can be bought via a variety of channels. Rehive recommends buying through a trustworthy exchange, as it’s usually the lowest-cost long term solution, but many wallets provide a fiat payment method via credit card.
Via an exchange
Exchanges are the best on-ramp for converting larger amounts of fiat into cryptocurrency. The downside is that they are usually region/KYC dependent. Rehive recommends using a trustworthy exchange to buy cryptocurrency for your Hot Wallet, or any other operational needs, to mitigate fees.
The exchange you choose will primarily be determined by the countries they support. For the US a few good options are:
Coinbase (https://www.coinbase.com/)
Kraken (https://www.kraken.com/). They do have support for non-US countries but overall access might be limited.
Otherwise, if your country has a known, trusted exchange that can handle your specific fiat currency, it is recommended to use them. It's important to use an exchange that actually allows you to buy real Stellar lumens and withdraw the Stellar lumens on-chain (not just crypto investment instruments).
Via a wallet
This is usually the easier but more expensive method. Many wallets provide the option to purchase crypto but will charge a fee for the service. On top of this, your credit card processor might also add a large fee to the transaction if they detect that it’s a crypto purchase. Wallets that support purchasing Stellar lumens are:
Lobstr (https://lobstr.co/)
StellarX (https://www.stellarx.com/)
You will need to register and create a wallet before buying the crypto with a credit card.