how to make your own flame without buying from other people and if we buy a flame always writing forged, forged what is it?

Go to the ingame main menu, click on setup > utils > flame forge.

In there, you can forge your own flame. But note that you have to pay to forge said flame, and the forge price is more expensive than the flame's price.

How much the prices?

The forged flame price varies from how complex the flame is

The cheapest how much?

I dont know for right, but i think its like 20k up.

I forget the actual number, but the cheapest flame ever forged was something like 33k, and the flame was invisible.