I strongly suggest to first wait for the VISA approval before proceeding with buying tickets for public transportation or attractions. There is no financial benefit if you buy them in advance. Furthermore, these tickets will not sell out. All you risk is to loose money.
In certain circumstances a refund is possible, however, there will be a refund administration fee which you can easily avoid if you wait until the VISA has been confirmed and all is set concerning your Schengen entry.