I have spent a long time working in software startups of various stripes, and I have also spent a long time working with Agile teams delivering software of various stripes.
It is difficult to sufficiently emphasize how similar those two models are. Think about it:
|What’s the simplest thing that could possibly sell?||Working Software over Comprehensive Documentation|
|Hire smart, talented people, and most of the problems will take care of themselves||Individuals and interactions over processes and tools|
|Get something out quick so your customers can give you feedback||Customer collaboration over contract negotiation|
|What you end up building is almost never what you originally envisioned||Responding to change over following a plan|
Read this fascinating article about Dropbox, and how it succeeded where its competitors did not. It should help you down this path.