Buy them as needed and according to your needs. Unless you are training yourself to be a mechanic - You can buy some nice quality set that will last.
Some, most sets will have tools that will work with some/most modern bikes...Your "vintage" bikes may use old standards, and you will need "vintage" standard tools for that. On the side note, there was not many things you couldn't fix with regular household tools

Do some more research, find out what tools your bike needs before buying any set.