The Arena is the best source of Gold and Units. By using your lower-tier champions (the ones you likely wanted to sell) to run streaks in the 1-star or 2-star arenas, you earn Battle Chips. These can be traded for Arena Crystals, which contain massive amounts of Gold. 2. Questing and Incursions
The champion’s Signature Ability is unlocked or leveled up. how to sell champions on marvel contest of champions
If you need ISO-8, focus on completing Event Quests or Story Quests. Duplicate champions from the crystals you earn here will provide far more ISO-8 than the old selling mechanic ever did. 3. Leveling for Prestige The Arena is the best source of Gold and Units