What are you building? What product or service are you building? And, for who are you building it and what problem or pain does it solve?
This isn't something you'll be building in isolation and there are 3 main components:
So what is the most minimal feature set you can build and develop
to provide to create gains and eliminate pains for customers from
day 1?
Also, let's take a look at forming your Value Proposition from 2 different sides:
As A Product Startup:
Which are part of your value proposition?
Which intangible products are a par of it?
What financial products?
Which digital products?
As a Service Startup:
What are the core services that are part of your value
proposition?
Which pre-sales or sales services?
Which after-sale services?