Hey there! When building a deck in Magic: The Gathering Arena, it’s important to have a clear strategy in mind. Start by choosing a win condition or a theme for your deck, whether it’s aggro, control, combo, or midrange. Make sure to have a good balance of cards that support your strategy, like removal spells, card draw, and creatures that fit your game plan. Don’t forget to pay attention to your mana curve to ensure you have a good mix of low-cost and high-cost spells. And always remember to playtest your deck to see how it performs and make adjustments accordingly. Happy deck building!