Assuming you already have a gun and optics/irons, there's not much more that you HAVE to have to go hunting despite what modern consumer culture would suggest. Other than possible blaze orange requirements for your jurisdiction, there's really nothing to stop you from going hunting in the clothes currently on your back. That might not be the most comfortable or effective option, but it's certainly possible and there's a strong chance that thousands of humans throughout history have hunted in even worse gear.
But if you want to make sure that you have the basics covered for at least a comfortable hunt, here are some suggestions (as well as suggestions for things you don't HAVE to have (because modern consumer culture is how I make money...)). Note--this is mostly geared toward everything but bird hunting, which warrants its own discussion later.
Footwear - potentially the most important piece of gear, depending on your hunting style. If western spot-and-stalk is your game then good footwear is a must...but that doesn't mean you have to go out and drop a couple hundred bucks on a rugged pair of Danner Boots (if you want to, though, they're great boots). Depending on your hunting terrain, maybe a pair of sneakers or trail running shoes will offer enough protection from the environment. If you're going to be tromping through dead branches and leaves you can add on a pair of lightweight gaiters to keep debris out of your footwear. For more rugged terrain (rocks, mud, water, snow) or trips carrying extra weight, maybe the support and protection of a hiking boot is the better choice. I recommend going for a waterproof boot--you might not always need it, but inevitably you will and if you buy it up front you avoid a second purchase...and wet feet.
Merrell makes great footwear that doesn't break the budget. If you want to splurge, the UA Ridge Reaper Infil Ops boots are amazing. As light as a pair of trail runners, with incredible support, protection, and durability. Hundreds of miles on mine.
Shirt - you don't HAVE to have camo. Humans have hunted for millennia without camo. I spent a few hipster deer seasons hunting in a plaid Abercrombie & Fitch wool coat over a flannel shirt. But camo can make you more effective and most likely your torso will be more visible than your legs so it's the place to wear camo. Most important, in my opinion, is being comfortable because the more comfortable you are the more hunting time you can muster. I usually go with a light weight merino base layer under a long sleeved shirt. If you're hunting in cold/winder conditions it's wise to avoid cotton due to the heightened risk of hypothermia; if you're hunting in hot, dry, desert conditions then you actually might want to wear cotton or merino to keep your sweat on you for prolonged evaporative cooling.
Pants - pants are more environmentally dependent than a shirt: is it going to be hot? wet? are you walking through long grass? through briars or cacti? If you want to pull something from your closet, I generally would recommend khakis/chinos over jeans. I've done a lot of hiking and hunting in khaki pants and have been very comfortable because they are lighter and more movable, but still are bulky enough to protect from abrasions. They're breathable and will help keep your legs from getting hot and sweaty--but if you're in a wet environment any cotton pants are going to soak up water and get heavy and sticky and miserable. On the flip side, synthetic pants cut weight and dry quickly, but many of them aren't as breathable and don't provide quite as much protection from things that want to poke and scratch you. Unless you're hunting a stand or extremely cold weather, I'd avoid fleece lined pants in favor of a base layer because if it gets hot you can take off a base layer but you can't remove a fleece lining.
Kings and Carhart will get the job done. If you can splurge, Under Armour field ops pants are my favorite general use hunting pants--they're rugged but breathable and offer great protection for busting through the desert; or the Ridge Reaper Raider pants for days of hiking through the woods in Northern Arizona.
Jacket - again, there's no real reason why any old jacket that's sufficiently warm can't work for hunting. My
Prana Bronson jacket would easily convert from a casual daily jacket to a cool-weather hunting jacket. Weight and packability are the primary considerations and tradeoffs when using something from the closet. Down is going to be the lightest and most packable, but if it get wet it's basically useless. Synthetic (primaloft being the gold standard) is reliable for all conditions, but it's going to be heavier and bulkier. Also think about how active you'll be when deciding whether and how much to insulate...maybe layers are your friend instead of a big puffy jacket. When I went on my 2018 elk hunt there was 8" of snow on the ground, constant wind, and temps rarely got above 35...but I was constantly hiking so I usually only wore a lightweight jacket over a merino long sleeve shirt with a windproof vest keeping my core warm; then when I stopped to glass I'd throw on a down coat under a windproof coat to keep my temperature up. It was a lot to carry, but it was the only way I could keep from overheating while hiking or freezing while stopped. Unless you have the shortest walk to you hunting stand, layering is going to be your friend. Consider a fleece or hoodie layer to wear on its own for moderate cool temps, a soft shell layer for cooler temps, and both of them for cold temps.
Socks - I have a hard time recommending anything but Darn Tough wool socks. They're a bit of a splurge at $15-25/pair, but what other socks do you know that come with a lifetime warranty? I have pairs still that I've worn for over ten years and other than loosing a little bit of plushness, they're still as good as a brand new pair. Wool socks are your friend when hunting--they'll keep you warm if your feet sweat or you step in a puddle, they are anti-microbial to keep everything from stinking, and they're damn comfortable.
A knife - its not clothes, but you can't harvest animals without a knife to field dress and butcher them. And in general I never go into the woods without a knife. On a budget, Moraknife has to be the way to go. People love that knife. It doesn't do it for me, but for under $20 and a 5 star rating after over 13,000 reviews it appears that I'm the outlier. I have a couple nice SOG huntspoint knives, some good Gerbers, and a few neat CRKTs; but my brand of choice is always Benchmade (though it's far from a budget knife). A drop point blade is ideal as it helps you in gutting an animal without puncturing the stomach with the knife tip. I generally prefer full-tang, fixed blades for greater use in potential survival situations; but a good folder can go a long ways.
Those are the true essentials that you need to get out the door. Depending on personal preference and the requirements of your hunting conditions you might need some other things like gloves, a hat, etc.
Gloves range from protection from vegetation to protection from the elements. When I'm on the move in the woods I frequently wear mechanix work gloves over a merino liner glove--I alternate multi cam and blaze orange depending on my hunt. On my elk hunt when it snowed I ran a goretex shell over merinos. I haven't found a glove that works well for stationary hunts because my hands are too big for most gloves and I don't feel like spending the money on the ones that do fit for just a week or two of hunting each year. If I was buying something right now I'd go with deerskin for a better tactile experience.
Hats for me are a statement of personality in addition to function, but I'm kind of addicted to hats. Usually I'll wear a baseball cap to block sun, and pair that with a beanie when I need warmth. Not much else to say about hats, other than keep in mind whether you want or need to wear blaze orange.
Buff/neckwear - in cold weather it's nice to have something on the neck for warmth. In hot, sunny weather it's nice to have something on the neck for cooling and sun protection.
I am BIG into hot weather hoodies these days for hunting and fishing. It's my adaptation of Arab robes in the desert, which I've tried to emulate in my own way since visiting the Middle East years ago. A loose fitting hoodie provides shade, it fits loosely on the skin permitting a cooling breeze, and the hood replaces a buff for the neck. Bamboo is my ideal fabric, but I have both a threadborne and an Anvil cotton hoodie and both work great (the Anvil is also my go-to summer yard work shirt).
Backpack - not a requirement by any means, but you'll probably be carrying layers, lunch, and water...if you can do all that without a backpack, please tell me your secrets. The big choice here is whether you will need to be able to pack out meat on your backpack or if you can get a vehicle to your kill. If you need to pack out then a frame pack or load shelf are going to be helpful but not necessarily required.
I could keep going forever because I love gear and there are so many options to choose from. Head lamps, flash lights, gaiters...but this will get you started and then some. If you want further recommendations shoot an email to getthefunout@gmail.com and I'll be thrilled to talk gear with you.
