How to smith a weapon with the best legit damage possible?

I know you can use a grindstone to make weapons legendary but ive seen people use potions and enchanted armour/jewelry.

I want to know how to get everything to make the best weapon i can.
Like what kind of potion, do i need to make the potion with enchanted armour, and what kind of armour do i need to wear along with the potion on the grindstone etc.

It's not exactly "legit" because oftentimes, they're using the enchanting glitch to get insanely high percentages put into the smithing. If you want to have a weapon that's actually legit, without abusing the system, you'll need to find, make, or buy the most powerful potions and enchanted items you can, to boost your smithing skill. (I think the highest is something like 60% from a potion, and 40% for each enchanted item.)

Yeah, I know about that glitch, but at the end of some videos where they get say a unique weapon or something, they upgrade it on a grindstone but before they drink a potion and put on certain armour and then they upgrade it.

I want to know how to get that potion and how to get the armour.

Im sorry if i didn't make sense in my original post.

They're doing exactly what I said, though. They've got specific armor for smithing, that has either been found or crafted, which has the smithing skill enchantment. And the potion has the same effect, it's just temporary.

You need:
100 Smithing
100 Enchanting
100 Alchemy
Perks in Smithing up to Dragon Smithing(Going up the Left side gets you there faster)
Perks in Enchanting:
Realistically you only need to max out Enchanter(first Perk, 5 ranks)
Perks in Alchemy:
Alchemist(5/5), Physician, Benefactor

You're also going to need several sets of gear you dont care about, have unlocked the fortify alchemy and fortify smithing enchantments, and have ingredients for fortify enchanting potions and fortify smithing potions.
You're going to want to make a fortify enchanting potion(or a few of them)
Then go to an enchanter and drink the potion. Then enchant a set of fortify alchemy gear(head, gloves, ring, necklace if I remember right)
Then, wearing your new gear, head to the alchemy station and make another fortify enchanting potion.(It will be a higher percentage than the previous one)
Keep chaining this together until the percentages stop getting higher.(There is a cap)

These numbers can get even higher if you are a vampire and you get the necromage perk in restoration(not a glitch or exploit, game mechanics)

These numbers can get even higher if you have the Dragonborn DLC and you get and wear Azhidal's armor to get the Azhidal's Genius perk which grants a boost to enchanting(wear the armor while using the enchanter)

After getting the best fortify alchemy gear you can get, make another set of fortify enchanting potions and a set of fortify smithing potions.

GO to the enchanter, drink the fortify enchanting potion(s) and make a set of fortify smithing gear(Body, Gloves, Necklace, Ring if I remember correctly.).

Finally go to the forge and DO NOT DRINK THE POTION YET.
Make whatever weapon you want out of dragon bone(you have dragon bones and scales right?). For the highest damage, make a warhammer.

NOW, drink the potion and make sure you are wearing your fortify smithing gear. Temper your weapon at the grindstone and it will be at maximum damage.

To get an even higher damage: max out the appropriate weapon skill(2-handed for a warhammer) and wear the appropriate maxed out fortify weapon skill gear(you know how to make maxed out enchantments by now).

Now enjoy crushing everything in the game,

Thank you so very much, ive been looking for this information for years! And thank you too, grapefruit.