Why upgrade a staff? When you upgrade your staff, not only do you get increased Durability to fire off even more projectiles, but you also gain longer debuff times for debuffing type staffs, or more damage for damage type staffs! The higher tier the staff, the more durability and debuff time added per upgrade! Lets take a look at the tier of staffs:

• Pine Staff:Power of 1
• Birch Staff:Power of 2
• Spruce Staff:Power of 3
• Oak Staff:Power of 4
• Onyx Staff:Power of 5
• Elm Staff:Power of 6

What stats get upgraded? The 'Attack', 'Durability', and 'Debuff Time' are all upgraded each time you enhance a Staff. A Pine Staff being the lowest tier staff would give the lowest amount of increase per upgrade while an Elm Staff would give the best. You will also gain some extra durability that scales with the upgrade level. The amount that is added per upgrade is as follows:

• Pine Staff:
  • Attack:+1
  • Durability:+25
  • Debuff time:+0.2 seconds
• Birch Staff:
  • Attack:+2
  • Durability:+50
  • Debuff time:+0.25 seconds
• Spruce Staff:
  • Attack:+3
  • Durability:+75
  • Debuff time:+0.3 seconds
• Oak Staff:
  • Attack:+4
  • Durability:+100
  • Debuff time:+0.35 seconds
• Onyx Staff:
  • Attack:+5
  • Durability:+125
  • Debuff time:+0.4 seconds
• Elm Staff:
  • Attack:+6
  • Durability:+150
  • Debuff time:+0.5 seconds

You can quickly see how dust can begin to stretch further than, for example, a Tin Chaos Sword with its 40 dust rate. The above info does not include the extra durability obtained per upgrade.

Tips

• While staffs can be used to save dust in comparison to lower tier weapons, its important to keep in mind that upgrades can fail and consume the dust anyways, leading to decreased dust rates due to getting nothing out of that dust.