I used math.random but my code isn't random?

This is because math.random is NOT ACTUALLY RANDOM. It is based off it's seed, but I don't know what it does with the seed. To make this different every time, use

math.randomseed(tick() * wait() / wait())
local morerandom = math.random(15, 30)
local stone = math.random(1,morerandom)
if stone == 25 then
    (Code here)
end

Hope this helps!

First, you need math.randomseed(tick()) math.random() in one script that runs at the start of your place (and is never run a 2nd time). If you initialize a randomseed more than once, you'll reset how the random numbers are generated. ex, if you run the following script multiple times, it will always print out the same 3 values:

math.randomseed(1)
print(math.random())
print(math.random())
print(math.random())

--Output:
0.56358531449324
0.19330423902097
0.80874050111393

So if each of your scripts tries to call math.randomseed and then you ask for a random number (or several random numbers), they will always turn out to be the same.

But if you do this script:

math.randomseed(tick())
print(math.random())
print(math.random())
print(math.random())

It will print out different values each run (so long as you start each run during a different second -- otherwise tick() will return the same thing). However, you might notice that the first value is similar each time. This is why you should always "throw away" the first random value after using randomseed. and is why the math.random() can go right after the call to randomseed.

As for your script, some notes:

• Using morerandom doesn't really do anything. If you want there to be a 10% chance of something to happen, for instance, you should just do if math.random(1, 10) == 1 then or if math.random() <= 0.1 then
• You call :Clone() on line 7 but don't do anything with the result (which just destroys the Clone), though you probably don't need the line anyway as you already cloned something on line 6
• Note that you're supposed to assign the parent last (as it is significantly more efficient to assign the CFrame first, then set the parent). In this case, that means right before you destroy script.Parent.

There are some official strategies for getting that extra-randomness you are looking for. The use of two variables is creative, but I'll leave it to the math people to explain why it's not very random actually (I don't know the specific reasons).

http://wiki.roblox.com/index.php?title=Random_numbers#Generating_Different_Random_Numbers_Every_Time_the_Game_Runs

To receive a different value every time the function is called, you need to set the seed to a different value when the game runs

math.randomseed(tick())
  

That at the beginning of your script should make it more random.

I've always had this problem, but it's very easy to fix. Just add math.randomseed(tick()) at the first line of your script to change its seed. This means that the seed that generates the "randomness" changes to "make it more random / actually random".

math.randomseed(os.time())
local morerandom = math.random(15, 30) 
local stone = math.random(3, morerandom) 
print(stone) 
if stone == 17 or stone == 5 then 
    stoneblock = stoneblocksetup:Clone() 
    stoneblock:Clone() 
    stoneblock.Parent = script.Parent.Parent 
    stoneblock.Name = "Rock" 
    stoneblock.CFrame = script.Parent.CFrame 
    script.Parent:Destroy() 
end 
script:Destroy()

BTW i tried it with math.randomseed(tick()) and it worked fine but try this instead