For starting off, I'd not get too hung up over ultimate sharpness. As the other folks have said, there are many lenses which will give you excellent results without spending mega-money. Not to mention that compared to 35mm (is that even possible?) 4x5 is hugely forgiving.
However, you are probably better off sticking with shuttered lenses, at least until you get used to all the mechanics of working with the camera.
Finally, welcome to the large format world!
AT this phase of your decline,
it's probably more important from WHOM you buy the lens
than WHAT you buy. Get it locally,
from someplace to which it may be returned.
Don't worry over scratches, stuff like that.
"One of the painful things about our time is that those who feel certainty are stupid,
and those with any imagination and understanding are filled with doubt and indecision"
ANY lens in a 4X5 format that is marginally better than a coke bottle cramed into a lens board will blow you away. You don't really know what's good or bad yet, until you experience the lens. Don't think you will only have one lens the rest of you life... you will change or add lenses as you learn what is good and bad but you need a reference point to begin with.
To look at a favorite photographers images and learn what equipment he used and duplicate it will not make you a good photographer.
For a guy beginning, the most important consideration is the shutter, not the lens. Get something in a low mileage Copal shutter so that you can be assured that the problem isn't inconsistent operation. I started with a Caltar SII 210 f5.6. It was pure luck but it's what came with the Cambo I traded a P67 for. Turns out it was a multi-coated Symmar in Caltar wrapper, and a lens that could resolve high 60's line pairs. Later on you can stray into all sorts of interesting old junkers with packard shutters behind them, but don't start there. Any Caltar in a black Copal would be excellent to start out with.