Start with a small level with great shaders and grafics. YouŽll get an instant impression on how your game will look like. It will help you to develop a style.
i guess he COULD work on gameplay after he did set up a small decent looking scene but setting up a decent looking scene isnt exaclty easy, atleast if he gets his content done correctly, an artist might see potential and be willing to help, care should be put into how the game feels.
DonŽt use placeholders, because youŽll struggle when it comes
to polycount & texture sizes. On top of that, youŽll have to do 50% of the level design twice. Unnecessary additional work, imo.
-First focus on grafics, because actually you want to attract people at the very first beginning to make them curious.
Well said in another thread: They are coming for eye candy, they are staying for content.
sorry i personally dont believe in alot of this AT ALL, first off, if he doesnt use placeholders, what does he do until that miraculous day come when he finally gets that boat model he wanted, dont SHOW us your placeholder, use it to get a feel for your game, ofcouse we dont literally mean using a box, but he can use some lowpoly free boat model for now, personally i think he's already failed if he spends two days tweaking graphics and then all we see is some halfglory screenshot
My project works this way and it evolves better than IŽve thought at beginning.
But (!!) in the end youŽll to extermine your workflow by yourself. Because it will differ and depends on the project, your skills and your budget (time & money).
not everyone has your potential
yes i was the one that said people come for eyecandy and stay for content but good gameplay falls under eyecandy also, ofcouse by placeholders we do expect it to have a basic look of the game:
for example,
this is the start of scion using placeholders, first thing i do when i start a project is get it working, if your game can impress people using no shaders and placeholders then youre on the right path, someone WILL step forward to assist, artists tend to rather put their work in something that seems fruitful and i dont think a placeholder is necessarily ugly, as long as it provides whats needed to start working, a fully animated model can also be a placeholder, as in:
this is a few months later:http://www.youtube.com/watch?v=sZNo51EIG8Mthen few weeks:
then we got to here:http://www.youtube.com/watch?v=o4isYeoyw9c 
your method works in some situations, i just dont see why someone with low resources should spend days/weeks trying to make eyecandy, some water, a terrain, skybox, free boat model and some sprites seems enough for him to make something that would appeal to people IF he did gameplay right
