Cotton kills.
Fleece burns (quickly)
Wool itches.
I like Cabela's Thermax long johns (top & bottom) wool shirt, fleece top and bottom and my 'Don't Shoot Me" orange bibs with a shorty orange bomber jacket. Polypro under wool socks in Sorel Boots.
I carry the fleece top and the bibs on the walk up the mountain and put them on immediatly when I reach my stand. You've got to trap the body heat that you've built up by walking.
Layers are the key. If it gets warm, you can remove a layer. Cold, you can add a layer.
One year it was cold (low teens) on the first day of our hunt. The second day the temp went up into the 50's. I had dressed for the previous day's weather and wore my bibs over my long johns. I couldn't take the insulated bibs off because I had no pants underneath. Thought I would melt by the end of the mile and a half hike out!
So to answer your questions...
Is wool better than synthetics?
yes, but not absolutely necessary...NO cotton
Is a 4-in-1 jacket that much of an advantage?
If you don't have sweaters or similar layers yes. Otherwise not really.
Do I really need camo pants or can I get away with just a camo jacket and some brown or green pants?
Subdued earth tones are enough. BUT if you are gun hunting do everyone a favor and wear some blaze orange.
Are bib overalls necessary?
Personal preference. I like them because you don't get that draft at the small of your back when you sit.
Is gore tex all that?
I have an Eddie Bauer parka that's 3 years old and still going strong. But I don't wear it hunting. It is noisey and I'd rather not hunt in the rain. For emergency rain wear I carry a poncho...to walk back to the truck in

Is it just me or is real-tree ridiculous looking outside of a forest?
Here's where I'll get flamed. IMNSHO Realtree and its clones look good on the rack, not in the woods. They visually blob at a distance and you can still see the man silhouette. I prefer large areas of color that break up the man shape. My all time favorite is the Italian Army pattern, but that is way hard to find.
The WW2 Marine pattern is good (look at the water fowling camo in the Cabela's catalog it is similar) as is the NATO woodie pattern. In pine forest the VN Tiger Stripes work well. Plain white in snow is amazing. Old time hunters wore red and black lumberjack plaid. Red for the other hunters, and big blocks of contrasting shades to hide the man shape from the deer.
Always check your background, you don't want to be skylined or be dressed like a bush in front of a rock. The line of your head and shoulders is a dead giveaway. You can break that up with a brimmed hat.
And Gary got it right when he said to sit still. I was very proud when a little bitty bird landed on the muzzle of my shotgun.
Good luck!