Lumi Master Team Building Basics
A good team is a set of answers, not three separate favorites. Choose coverage first, then make sure each member has a clear job when it enters the field.
Start with type coverage
Check your lead's weaknesses on the type chart, then add partners that can enter safely against the types it dislikes. Dual types can change a matchup, so use the calculator rather than relying on one badge.
Coverage is more useful than a fixed rule about any single tier. A lower-ranked Lumi can be the correct choice when it answers the encounter in front of you.
Give every slot a job
A simple early composition has an opener, a response to its bad matchups, and a flexible third member. Read trait text and skill cost before assigning that role.
Avoid members that all require the same setup unless you already know the fight allows it. An inexpensive action or clean switch can keep a plan from collapsing.
Plan the switch
Before battle, decide which member takes over if the lead meets resistance. This prevents a reactive switch into another bad matchup.
Revisit the plan after unlocking more slots at exploration levels 5 and 8. The extra space is most valuable when it adds a new answer, not a duplicate weakness.
Run a three-slot audit
Before entering a battle, name the purpose of each slot: the lead, the answer to the lead's bad matchup, and the flexible third member. This makes a team easier to adjust when a new Lumi joins the collection.
Check the type chart from the opponent's likely attack into each of your members, not only from your own attack outward. Then confirm that the skills you plan to use have costs that fit the rotation.