+1 for a good quality repair stand. A set of good quality metric Allen keys is a necessity as are good cable cutters. Note the emphasis on "good". Don't buy shoddy tools, they will waste your money and damage your bike.

Beyond the normal tools you already have like screwdrivers, pliers, etc. the specific bike tools will depend on the make and models of your components. Buy what you need as you need it. Pre-made kits will contain a lot of obsolete tools.