Two numbers make your output
Your attack has two halves. Damage is how hard each tear hits, and tear rate is how often you fire.
Multiply them and you get your rough output. Raising either one helps, but both together help most.
Raising damage
Damage items make each tear count. A single strong tear can clear a small enemy in one shot.
Damage also scales with replacements like a charged attack. A bigger hit rewards waiting for the shot.
Raising tear rate
Tear rate items let you fire faster. More tears per second means more chances to hit.
Fast tears help against enemies that dodge. They also keep pressure on a boss between its attacks.
When the two trade off
Some items raise one stat but lower the other. A big tear that fires slowly can feel worse in a swarm.
Read the trade before you take the item. Ask which enemies give you trouble and which stat answers them.
Next: Item synergies basics and Boss patterns.