Out-of-Date MS SQL Server 2014 instance Could you give me some advice on the best practice to update a SQL Server 2014 instance that is on version 12.00.2000.00? Can I install the Service Packs or do I need all of the cumulative updates as well?
Install the most recent service pack, then install the latest cumulative update.

According to SQL Server Builds, the most recent Service Pack for SQL Server 2014 is currently SP2.

CU10 is the most recent Cumulative Update.

Ensure you take a backup of your databases onto physically different media, and do this in a non-production environment to test the change prior to doing this to your production SQL Server.