In Onslaught , we took that idea to the next logical conclusion: Rather than have a creature grow based on a certain creature type, these creatures were defined completely by the creature types
Unlike Sower of Temptation & co., Agent plays for keeps with an ability that persists even if it leaves the battlefield
Over all Vastwood Seer is top range filler
You add just two counters on your blue planeswalker, because Doubling Season specifically says you only get double counters from an effect , and adding loyalty counters to activate a loyalty ability is a cost , not an effect
If you dont remember what was said there, I highly recommend reviewing it, but the super short version is that you count your mana symbols, figure out their ratio, and then apply that ratio to the number of lands you plan to play