Mana ramp involves finding ways to get more of your lands onto the battlefield as quickly as possible and/or creating reusable sources of mana through permanents on the battlefield
Act of Treason will wear off even if you activate Obeka to end your turn, because you're literally ending your turn, and there's not return trigger attached to Act of Treason
Meanwhile, Injury is a strictly worse version of a very old common named Lunge, which has the exact same effect as Injury but at instant speed
Oh, did I mention that this card is a fantastic Ephemerate or reanimation target
If you tap a forest for mana, you get two green mana
Besides the New Year Treasure, the most valuable tokens are: Japanese Dominaria United promo Beast token at over $65 Southeast Asia Brothers' War promo stained glass Construct token at over $60 Southeast Asia Dominaria United promo stained glass Soldier token at over $60 Magic Player Rewards Saproling token from 2001 at around $50 Japanese Dominaria United promo Dragon token from 2022 at around $50 See the full list of valuable tokens on Scryfall