OK, so it's not really a strategy, just three options I think you should consider when creating a new digital service.
If you're looking to create a new application the best place to start is finding someone who's already made it and willing to share the code. There's increasing number of public sector organisations on GitHub all round the world.
Last year I wrote about an Kickstarter for local governments. As collaborative working becomes easier and professional networking more prevalent this is increasingly becoming an option, however I've yet to see a platform that will really enable this.
LGMakers will shortly be releasing help on how to share stuff, including the issues you need to consider and the practical steps on how to use GitHub.
Let's face it, it's not always possible or feasible to borrow or build but even if you have to buy something there are certain things you can look for.
GDS have a good guide on open standards and Warwickshire County Council's Applications Strategy is an example of including open standards in an ICT Strategy. Anything you buy should be build to open standards to enable it to be integrated with other stuff you borrow, build or buy.
So "Borrow, Build, Buy. It's not so much a procurement strategy, more of an attitude to application creation.