The Spike This time last month, copies of Faces of the Past were, remarkably, selling for just $1.87
Fun fact - this is the same as the standard MTG card size, and you'll see cards with similar dimensions in the Pokmon TCG too
This article will go through the basics of building a deck: choosing a commander, establishing a theme, optimizing mana curves, and other important tips
Gold is the more abundant currency, and will generally be earned by completing daily and weekly quests and filling out the battle pass (of which there is a free and premium version)
On the other hand, if you plan on building your own deck and strategy and just want some solid cards you can use in it, go with Amber/Emerald