What is the easiest way to Randomize randomizations?

You could make a table of possible choices, and retrieve them using a function whenever you need them.

local choices = {25, -25, 50, -50}

local function rand ()
    return choices[ math.random( #choices ) ]
end

print(rand(), 1, rand())
--Vector3.new(rand(), 0, rand())

While ImageLabel's way is very correct, I am going to go into further detail, and create a table of random numbers.

So first,

let's start by creating a table that will hold all of our numbers.

numbers = {}

Great,

now we can setup a function that's going to generate our table. Additional detail will be given in the comments.

function GenerateTable()
    checkNumber = false -- We will set this to true if the number already exists. Won't happen commonly, but just in case.
    for i = 1, 50 do -- Generate 50(ish) random numbers
        for _,v in pairs(numbers) do
            local randomNumber = math.random(0,100) -- Our random number
            if randomNumber == v then
                checkNumber = true --Uh oh, already exists. This is where the 50(ish) comes into play. If this happens, it will only generate 49 (unless it happens multiple times. Very unlikely).
            end
        end

        if not checkNumber then
            table.insert(numbers, randomNumber)
        end
    end
end

Now

that we have a random set of numbers, about 50 of them, we can refer back to ImageLabel's answer for the rest.

function generateNumber()
    return numbers[math.random(1,#numbers)]
end

Note: This is all from general knowledge, none of this has been tested, and this is not the most efficient way. This is just a way to get you thinking.

Hope I helped.