To ensure you attain the TRUE AVENGER status while using the "Add Bricks" option I advise you set it to add 10,000 bricks then add enough to stay just below the number needed to reach 100% the limits are as follows
Level - bricks needed
Struck off the List - 150,000
A Loki Entrance - 105,000
RAIL Hydra - 200,000
Shakespeare in the Park - 150,000
Helicarrier Havoc - 140,000
Avengers Assemble - 160,000
Earths Mightiest - 150,000
Lack of Insight - 80,000
Ready A.I.M. fire - 100,000
Lost in the Aether - 360,000
No Strings on Me - 170,000
Anger Management - 80,000
Korea Prospects - 140,000
Rise of Ultron - 120,000
Ultron Undone - 260,000
For example A Loki entrance needs 105,000 so add around 90,000 with the trainer and then it is easy to attain the other 15,000 through playing the level.
Hope this helps you all become True Avengers.
[Edited by Samiel, 2/3/2016 7:05:04 AM]