There is a lot of good advise in this thread. I will just throw out some points.
This is a good time of year to buy upland gear. Season is over or closing (preserves will be open till March) and there is Christmas overstock left over.
Sierra Trading Post, Sportsmans Guide, and other liquidators often have good upland stuff on deep discount.
I have some McAllisters waxed cotton gear, which is cheap compared to the other big names and now apparently out of business. I like it good enough.
Cabelas had an 8-in-1 vest/jacket/coat which got rave reviews. They have continued to raise the price of it every year, outpacing the rate of inflation. It was def worth it at $60, not sure it's worth it now.
Filson tin cloth is more durable than Barbour, but I (personally) think Barbour look better so I can also get double duty wearing it everyday. It will sort of make you look like a city slicker though.
Filson double tin pants will damn near stand up on their own.
There is a robust debate about upland pants vs chaps. Chaps are cheaper, but a little weird to use and get used to. Advantages are that on a three day hunt, it's nice to put on a clean pair of jeans each day. Also, if you regularly wear nice jeans or khakis, once they get too worn out for your day job, you can do yard work in them and just throw on a pair of chaps for hunting.
Mountain Khakis have a double thick pant, the Alpine Utility I think, which does a pretty good job for light brush, cornstalks, and small briars.
There are a lot of fancy upland hunting coats/jackets. I can't shoot worth a damn in any of them. Don't overlook a hoodie (orange ones are easy to get), an old school heavy wool shirt, or a heavy wool sweater (European military surplus). I find them 10 times easier to shoot in. I haven't tried any of the new "technical" or soft shell upland jackets.
Seriously consider wearing suspenders or bibs.
You won't need as much warmth as you might think for the actual hunt, as chasing a dog around is about the most active hunting there is.
Get a good set of thin, wicking, thermal long undies.
Front load game pouch is easier to load than rear.
Don't forget about Colombia for upland gear. They make some premium level stuff, everyone forgets them, and then it gets marked down. I second the suggestions about LL Bean stuff. A lot of the Bean gear has slipped in quality, but the upland stuff is pretty good, often discounted, and they will 100% stand behind everything they sell. I wear their brush pants.
Strap vests are really useful and versatile. Then, if they aren't made right or fitted right, you put your gear and a few dead birds in them and they slide off your shoulders every ten steps. But I hunt out of one.
Boots are really a personal choice.