({5} magic symbol) ({G} magic symbol) ({G} magic symbol) ({U} magic symbol) , plus an additional ({1} magic symbol) if Mystic Reflection was not foretold available.
Steps
Cast Avenger of Zendikar by paying ({5} magic symbol) ({G} magic symbol) ({G} magic symbol) .
Avenger of Zendikar enters the battlefield, triggering its ability.
Holding priority, cast Mystic Reflection by paying ({1} magic symbol) ({U} magic symbol) , causing the next creatures or planeswalkers to enter the battlefield this turn to enter as copies of Avenger of Zendikar.
Resolve the Avenger of Zendikar trigger, creating a token copy of Avenger of Zendikar for each land you control.
Each Avenger of Zendikar enters the battlefield, triggering their abilities.
Resolve an Avenger of Zendikar trigger, creating a 0/1 Plant creature token for each land you control.
Repeat step 6 for each remaining trigger.
Activate Goblin Bombardment any number of times by sacrificing any number of creature tokens, dealing that much damage to any target(s).