How to make a script that will make a player wear a uniform?

I need a script that will actually make a player wear a uniform depending on his rank in a specific group, and wear an helmet depending the group. I actually have, in the serverStorage, a folder "Uniform" and inside it theres the folder 'clothes' that actually contain all the clothes of the different legion/rank inside this legion (As 104thHrPants / 104thHrShirt / 104thPants / 104thShirt) and a folder "Helmet" (104thHrHelmet / 104thHelmet) <-- each of them have their specific clothe ID. Hr Rank start at '100'

RegShirt = game.ServerStorage.Uniform.Clothes.RegShirt
game.Players.PlayerAdded:connect(function(player)
    player.CharacterAdded:connect(function(character)
        if plr:GetRankInGroup(2772068) > 100 then
            player.ClearCharacterAppearance()

            player.LoadCharacterAppearance(RegShirt) 
        end
    end)
end)

In a past request someone has gave me this script, but it doesnt make the player wear the shirt/pants over and doesnt make the player wear the Helmet (The helmet is not in the catalog)

This is one, rather than wasting storage by putting shirts and pants there. For hats, I can't help you:

local shirtid = 0 --Add the ID of the shirt here
local pantsid = 00 --Add the ID of the pants here

game.Players.PlayerAdded:connect(function(plr)
	plr.CharacterAdded:connect(function(chr)
		if plr:GetRankInGroup(2772068) > 100 then
			local shirt = chr:FindFirstChild("Shirt")
			if shirt then
				shirt.ShirtTemplate = "rbxassetid://" ..shirtid
			else
				local nshirt = Instance.new("Shirt", chr)
				nshirt.Name = "Shirt"
				nshirt.ShirtTemplate = "rbxassetid://" ..shirtid
			end
			local pants = chr:FindFirstChild("Pants")
			if pants then
				pants.PantsTemplate = "rbxassetid://" ..pantsid
			else
				local npants = Instance.new("Pants, chr")
				npants.Name = "Pants"
				npants.PantsTemplate = "rbxassetid://" ..pantsid
			end
			--If you want to remove T-Shirts, then leave this code. If not, then erase that
			local tee = chr:FindFirstChild("ShirtGraphic")
			if tee then
				tee:Destroy()
			end
		end
	end)
end)

Here is a revised answer. Adjust this to match your needs

-- @author itsJooJoo
-- @author Narrev

local ShirtId = 0
local PantsId = 0
local RemoveTShirts = true
local RemoveHats = true

local Hat = script:FindFirstChild("Hat") -- Put directory of hat here

game:GetService("Players").PlayerAdded:connect(function(Player)
	-- Run each a time a player joins
	Player.CharacterAdded:connect(function(Character)
		-- Run each time a player spawns
		if Player:GetRankInGroup(2772068) > 99 then
			local Shirt = Character:FindFirstChild("Shirt") or Instance.new("Shirt", Character)
			Shirt.Name = "Shirt"
			Shirt.ShirtTemplate = "rbxassetid://" ..ShirtId

			local Pants = Character:FindFirstChild("Pants") or Instance.new("Pants, Character")
			Pants.Name = "Pants"
			Pants.PantsTemplate = "rbxassetid://" ..PantsId
			
			if RemoveTShirts then
				local T_Shirt = Character:FindFirstChild("ShirtGraphic")
				if T_Shirt then
					T_Shirt:Destroy()
				end
			end

			if RemoveHats then
				for _, Object in next, Character:GetChildren() do
					if Object:IsA("Hat") then
						Object:Destroy()
					end
				end
			end

			if Hat then
				local Hat = Instance.new("Part")
				Hat.BottomSurface = "Smooth";
				Hat.TopSurface = "Smooth";
				Hat.Size = Hat.Size;
				Hat.Name = "Hat";

				local Mesh = Instance.new("SpecialMesh", Hat)
				Mesh.MeshType = "FileMesh";
				Mesh.MeshId = robloxAsset .. Hat.MeshId;
				Mesh.Scale = Hat.Scale;
				Mesh.TextureId = robloxAsset .. Hat.TextureId;
				
				local Weld = Instance.new("Weld", Hat)
				Weld.Name = "HatWeld";
				Weld.Parent = ;
				Weld.Part0 = Character.Head;
				Weld.Part1 = Hat;
				Weld.C0 = CFrame.new(0, .5, 0);
				C1 = Hat.AttachmentPoint or CFrame.new(0, 0.3, 0.05);
				
				Hat.Parent = Character
			end
		end
	end)
end)