Well, I can say all wallets are easy to use but talking about the best is where the problem comes. One important thing to consider when choosing wallet is the security of your funds. In that case, I will recommend you the popular open source wallet which is Electrum wallet. It's easy to use and also use strong encryption for your phrase keys and your coins. I would also like recommend hardware wallets that are more secure such as Ledger Nano or Trezor. These wallets give you full control of your private keys but it will cost you some money and I don't know your financial strength and how long you want to hold your coins. However, your wallet security depends on how well you can secure your keys.

Secondly, buying bitcoin is not too hard once you have finished setting up your wallet. After generating your public address, you can use exchange P2P to buy bitcoin or from trusted vendors. In fact, you can buy it from this forum too but make sure you use escrow to avoid being scammed. Goodluck!