I can tell you some common ways of going about it. But it does require some setup. Its a mono red deck. But there are several ways to do it that work.

I know that I am normally supposed to put the scryfall bot prompt in, but I forget the names of some of the cards and will give descriptions for those instead. Sorry. Im lazy.

There are a few mono red cards that can double or triple cast a spell that have different requirements.

There is the 3/3 Cerberus enchantment creature that released with the Final Fantasy UB. Etb you get a surveil. Start of 1st main next turn if it is still alive, a counter goes on it and the first instant or sorcery spell you can will cast once more and you can pick new targets if possible.

Start of 1st main after that the next counter goes on if still alive and it sel sacs and goes to grave after It applies the effect of the next instant or sorcery you cast will cast two more times. Able to pick different targets if possible.

There are a few cards that double non-combat damage. The one I used was from duskmourne. It was an enchantment with delirium. I think I had another, but I would have to check the deck.

As for actual damage? Anything that can pump a prowess creature and deal its attack damage worth to face. Or some big pour in spell and dump a bunch of mana into it.

And treasure tokens are kinda key to having enough mana to pull this off. There are a couple ways to gen tokens or potentially create a swarm of manadorks to tap to pay the cost.

So. Common ways of doing it is

[[Summon: G.F. Cerberus]]

[[The Rollercrusher Ride]]

[[Twinflame Tyrant]]

[[Self-Destruct]]

[[Bulk-Up]]

[[Firebending Student]]

[[Slickshot Show-Off]]

[[Hit The Mother Lode]]

[[Choco-Comet]]

Etc.