From the Order of Chaos set
cards can, and have, sold for higher prices if graded or particularly rare
X can't be 0. Activate only during your turn
The Energy cards were some of the cheapest prizes on offer and, so, back in the day, it was really easy to get quite a few, and yet now it's quite the opposite, and they stand as some of the most stunning yet valuable Energy cards to this day
Theyre creatures that get stronger whenever you play a land card (think of land like the gas that powers your decks engine) and have incredible synergy with other card types, leading to a deck that will overwhelm your opponent
Its useful to know how far youre thinking about deviating in power level when taking a card that works with your current plan in some way, but at least in the beginning, a straight ranking system can go a long way