Your first team answers one question: why are stages failing? Early leaks point to cheaper placement, better economy, or a tank. Boss survival points to sustained damage or a better trait on your carry. Expensive units sitting unplaced point to economy support or perk upgrades. One leak ending a close run points to defensive value.
Start with a reliable damage unit. This unit handles normal waves and gives the team a reason to invest in traits and gear. It can be lower rarity on the banner if you can place it consistently and keep it for several stages. A damage unit with a role-matching trait can beat a higher-rarity unit that enters the board too late.
Add boss pressure after wave clear works. Bosses and high-health enemies expose teams that only clear small waves. If your carry clears normal enemies but bosses walk through the lane, build a second damage option or improve the carry through traits, perks, and gear. Damage uptime, range, and upgrade money decide whether more Gems help.
Run a tank or lane-stalling slot when leaks are ending runs. A tank earns its slot when it buys enough time for damage units to finish enemies. It is not a replacement for damage if the whole wave survives, but it can turn close losses into clears. If the team has no defensive option, one heavy wave can erase a run even when your carry has good damage.
Run support and farm units for the job they perform. A support unit earns its slot by making the rest of the team clear faster, survive longer, or hit a break point. A farm or economy unit earns its slot by helping you place expensive units sooner. Personal damage is the weaker test for these slots. A farm unit that lets you afford your carry earlier can beat another attacker that sits unplaced because the run has no Yen.
Upgrade the team in order of permanence. Spend serious Trait Shards, gear materials, and Gold on units that will stay in the lineup. Temporary filler units can get light upgrades if they help clear Story, while expensive rerolls and late gear belong on permanent roles. When a new banner unit replaces a slot, keep investing in the old unit only if it still fills a job the team needs.
Tier lists work best for role comparisons. Tier lists help identify high-ranking units, but a team of expensive units can fail if the account lacks placement money or support. A lower-ranked role unit can be the correct slot when it fixes the loss in front of you. Compare candidates for the same job, then run stage results to decide which job matters next.
Rebuild the team after major upgrades. A new trait can let one damage unit handle waves alone, freeing a slot for support. A perk upgrade can make expensive placements realistic, changing which units are usable. A crafted gear piece can turn a boss killer into the main carry. After each major change, replay the stage that blocked you and inspect the new failure before spending more.