You can buy more Bitcoin if you want as long as you can manage to keep and hold them for awhile while waiting for the bull season to earn a profit but I don't suggest storing it on Coinbase or any exchanges. It was a big mistake of using an exchange wallet as a storage wallet as you are making your investment close to losing as whatever will happen to the said exchanges like hacking, your funds will also lose. Just think about the security and it was best to have it in your control rather than relying on the security of the exchanger.