Spreading the stat line
The most common mistake is raising a little of every stat. A flat line scales nothing. One focused damage stat plus one defense stat clears waves a balanced line cannot.
Pick the tag your weapons share and stack it. Let the rest of the line support that one focus.
Buying without a plan
Panic buying the first strong-looking weapon wastes the shop. A weapon outside your tag does not scale and crowds out the one that does.
Buy weapons that share a tag. Spend the next visit on defense if the run feels fragile, not on a fourth unrelated weapon.
Standing still
Brotato punishes stillness. Bombers explode on contact and chasers surround a stopped character. Constant motion is the easiest survival stat in the game.
Kite the wave edge with a ranged weapon. A moving target takes a fraction of the hits a standing one does.
Over-upgrading
Upgrading a filler weapon burns materials you need for the anchor weapon or defense. Upgrade the weapon that runs the build, and only once it is central to it.
The pattern behind most losses is a build with no identity. Every purchase should either stack your tag or fix a survival gap; anything else is noise.
Read your stat line after each wave and ask whether the next purchase serves the plan. Runs end when the loadout stops answering the wave standing in front of it, not when the items look weak.
Where to go next
Read the shop guide for what to buy each visit. Then see best builds and synergies for the one-tag rule that avoids these mistakes.