Equipping your characters with the strongest Echoes is the best way to make them stronger. However, to unlock the highest rarity Echoes in Wuthering Waves, you'll need to level up your Data Bank.
How to LEVEL your DataBank EXTREMELY FAST in Wuthering waves
To level up your Data Bank in Wuthering Waves, you'll need to catch new Echoes or Echoes of a higher rarity than the one you already have. There are over 208 Echoes to collect (including their rarities), which can be overwhelming, so here's how to level up your Data Bank quickly in Wuthering Waves.
Your best friend for leveling up the Data Bank is the Echo Gallery, in the Data Bank menu. In the Gallery you can see every Echo in Wuthering Waves and the highest rarity you have acquired.
Use this to determine which Echoes you should focus on first, select them, then press the Track button to jump to their nearest location on the map. I recommend filtering the Echo Gallery list to show the Echoes with the lowest collection progress at the top, then working your way down.