(For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)
The characteristics of the door that wasn't cast are still ignored while the copy is on the stack, and when the copy resolves, the token it becomes will enter with the appropriate door unlocked
How much are Magic cards worth? Which Magic cards are worth the most money? What makes Magic cards so expensive? Believe it or not, these are the most-asked Magic: The Gathering questions on the internet
If you want something blunt and simple, try Brad Nelsons Abzan deck.
Do I control the permanent I want to sacrifice
While I'm disturbed at your lack of practice identifying the systemic forces at work, I admit the prowess that Zimone displays is exemplary for her current studies