Board Thread:General Discussion/@comment-24872999-20140510101731/@comment-24797141-20140522011144

The obvious part is that you need 1 spirit for the base, then 1 copy or a matching joker for each limit break.

It is best to starting merging copies for bonus right after the last limit break. So for Rares, this is level 40; for Super Rares, level 55. You can have better control and more chances for a critical merge (boosted exp and 2xBonus) by merging one copy at a time. The lower the ATK/SPD of a spirit the more copies it will take. Generally, this applies to spirits that are not really balanced between the 2 (high ATK/low SPD; low ATK/high SPD). For a balanced SR, you should need 8 or 9 copies for max bonus. For a balanced R, you should need 10 or 11. That is just copies for bonus, not limit break.