It depends on your strategy. The system has been fairly updated to ensure that both high-geared and low-geared players have a decent chance to win a season.
However, by default gearing your characters with your best weapon and shield is the way to go.
- Equip with the highest stats
- Equip with the best-tiered weapon (i.e. 5 stars)
- Equip with the best elemental alignment character, weapon, and shield