Initially, you asked about the Blockchain.com web wallet... It is worth noting that web wallets, such as Blockchain.com, are not the most secure way to access your bitcoins. This is because it is possible to accidentally end up on a fake website (called a phishing site) and lose your funds if you're not careful. However, if you still want to try a web wallet, you might consider Bitamp Wallet as an alternative. Bitamp is a user-friendly, open-source Bitcoin wallet that operates on the client-side and supports both legacy and newer addresses. You can find more information about Bitamp at the following link: https://www.bitamp.com/ or in their ANN thread.
While desktop wallets like Electrum are generally considered to be a more secure option, it sounds like using one may not be feasible for you at this time. In this case, a web wallet could be a good alternative for your needs. With a web wallet, you can easily generate a legacy address to receive funds from the casino and then transfer them to an exchange with just a few clicks.
Edit:
It looks like you have been able to get the Electrum wallet set up and running. If you want to receive funds, you can go to the Receive Tab and create a new Request. When prompted, make sure to select "Address" rather than "URI" in the options provided. Once you have done that, you should see your BTC address displayed in the window on the right. This address will start with "1" and can be used to receive funds.