How do i make a cloud particle come out of a players feet?

I decided to give this idea a go, though generally you should attempt to do your idea and ask about problems that you face, or ask specifically what you need to do to accomplish it. This would be in the ServerScriptService. This uses the default particle, which is a sparkle; you might want to change that for your purposes. You can also change the settings of the particle emitter.

game.Players.PlayerAdded:Connect(function(plyr) --when a player is added
    plyr.CharacterAdded:Connect(function(char) --when the player's character is added.
        local root = char:WaitForChild("HumanoidRootPart")

        --This creates the part that emits the clouds
        local partiemit = Instance.new("Part")
        partiemit.Name = "ParticleArea"
        partiemit.Size = Vector3.new(1,1,1)
        partiemit.Transparency = 1
        partiemit.CanCollide = false
        partiemit.Anchored = false
        partiemit.Parent = char

        --This welds the particle part to the character, meaning it will follow the player
        local weld = Instance.new("Weld")
        weld.Name = "ParticleWeld"
        weld.Part0 = root
        weld.Part1 = partiemit
        weld.C1 = CFrame.new(0, 1.25, 0) --Changes the offset of the part from the humanoid root part.
        weld.Parent = char

        --This creates the actual particle emitter. Will probably need to mess with these values!
        local parti = Instance.new("ParticleEmitter")
        parti.Name = "CloudEmitter"
        parti.Size = NumberSequence.new(2) --Changes size of particles
        parti.Transparency = NumberSequence.new(0.5) --Changes transparency of particles
        parti.EmissionDirection = "Bottom" --Makes the particles move down
        parti.Enabled = false
        parti.Lifetime = NumberRange.new(1, 5) --How long particles will exist
        parti.Rate = 5 --How many particles are generated
        parti.Speed = NumberRange.new(1, 1) --Speed at which particles will move
        parti.SpreadAngle = Vector2.new(1, 30) --Will allow the particles to spread out
        parti.Acceleration = Vector3.new(0, 0, 0) --Makes particles move additionally.

        parti.Parent = partiemit

        local hum = char:WaitForChild("Humanoid")

        --Is called whenever the humanoid changes. If the move direction is zero, it will enable the particle.
        --If not, it will enable the particles.
        hum.Changed:Connect(function(prop)
            if hum.MoveDirection == Vector3.new(0, 0, 0) then
                parti.Enabled = false
            elseif not parti.Enabled then
                parti.Enabled = true
            end
        end)
    end)
end)

Use particle emitter, and a script the checks when the walkspeed value changes

You need to define the player speed. if the player's speed is 16 or more then put the particle effect inside the character

With all respects...if you dont know how to do this then you cant make one, you cant just trust on ppl to give you exact script, if you really want to make a game then add efforts onto, it not just by free models. plus scriptingHelpers was to get help not to request someone a system. You will need to learn stuff to make a game if you want it to be sucessfull. if you keep doing this then you will NEVER be in the front page, if you want to do this without any work at all then thats impossible, if you want to only put a bit of weight onto your shoulders then hire ppl.