You can buy Ethereum from several cryptocurrency centralized or decentralized exchanges. It's all on your choice and what payment option you decide on. Accessing exchanges like Binance, BitMEX, Kumex, Huobi, Kucoin, IDEX, Uniswap and host of others should present you easy options of purchasing Ethereum and other cryptocurrencies. Should you prefer buying with fiat, you can try using a non custodial wallet like atomic Wallet to help you do this easily and effectively.