you need to play the game, if you cannot buy the normal heroes roster at 500 steel, you have the starter´s. You only have 4 basic heroes for free. The rest costs 8000 steel if they are not dlc.
standard let you choose the same free heroes but the others that are not dlc, are 500 steel, and the game gifts you like 2000 steel or something like that.
dlc heroes cost from 10000 to 15000 steel in both.