Why do you want to sideline your bitcoin during the fork? You will miss out on bitcoin gold. That may a loss for you. However, I won't suggest to buy altcoins using the bitcoin before the form and then buy bitcoin again using that alt after the fork. That's too much risky. If bitcoin price goes down, it will bring down the entire crypto market. So you may incur huge loss for this activity. Instead keep your bitcoins in a wallet where you have access to the private key and enjoy the free bitcoin gold. That's an wise thing to do. Otherwise cash out in fiat just to safeguard your capital.