[Fatt_Shade]

Go in your game folder, find items.txt, open with notepad/wordpad and ctrl+F `runic_staff`.
From there search for best option for you, depending what class you play.
For expl

runic_staff_rrr {
  category=o
  image=heroitem_runic_staff.png
  hint_config=object_item
  label=itm_runic_staff_rrr_name
  hint=itm_runic_staff_rrr_hint
  information_label=itm_runic_staff_rrr_info
  maphint=
  mapinfo=
  price=190000
  maxcount=0
  level=5
  race=neutral
  use {}
  mods {
    intellect=count,3
    sp_spell_attack=count,25
    rage=limit,15
  }

Is staff with 3 might runes hence runic_staff_rrr = 3 red runes, and it gives 3 intellect / 25% more basic dmg by spells / and 15 rage.

Listing more are all combinations for runic staff, but as for last lvl with 3 inserted runes is :
RRR = 3 might runes

    intellect=count,3
    sp_spell_attack=count,25
    rage=limit,15

GGG = 3 mind runes

    intellect=count,3
    sp_spell_holy=count,25
    leadership=count,5%

( 3 intellect , 25% bonus for order spells (resurrection, heal, etc) , +5% leadership)

BBB = 3 magic runes

    intellect=count,5
    mana=limit,15
    sp_mana_battle=count,2

(5 intellect , 15 mana , 2 mana/round like concentration skill).

Hope i helped a bit