I'd put "product idea" last only because if you have reasonable funding and are solid on the first 3, you'll figure out the product. Also with #3 it is really the whole team, but given founder(s) are probably the only ones in initially I say Founders skillset.
1. Complete transparency, 2. Solid business strategy, 3. Founders skillset, 4 Product idea.
I'd put "product idea" last only because if you have reasonable funding and are solid on the first 3, you'll figure out the product. Also with #3 it is really the whole team, but given founder(s) are probably the only ones in initially I say Founders skillset.