All gem effects throughout their tiers (1-10) - credits to zmhl3451:

- Ruby: weapon (+% fire element): 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. armour (+life): 10, 15, 20, 25, 30, 34, 38, 42, 46, 50.
- Amber: weapon (+accuracy): 15, 20, 25, 29, 33, 37, 41, 44, 47, 50. armour (+AC): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
- Sapphire: weapon (+% lightning element): 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. armour (+mana): 10, 15, 20, 25, 30, 34, 38, 42, 46, 50.
- Topaz: weapon (+% acid element): 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. armour (+resist all): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
- Amethyst: weapon (+% arcane element): 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. armour (+% life regen): 20, 24, 28, 32, 35, 38, 41, 44, 47, 50.
- Diamond: weapon (+% cold element): 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. armour (+ melee damage resist): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
- Sodalite: weapon (+% holy element): 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. armour (+% mana regen): 20, 24, 28, 32, 35, 38, 41, 44, 47, 50.
- Onyx: weapon (+% damage): 50, 65, 80, 90, 100, 110, 120, 130, 140, 150. armour (+ arrow damage resist): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
- Spinel: weapon (+ minion damage): 5, 7, 8, 9, 10, 11, 12, 13, 14, 15. armour (+ minion life): 25, 30, 35, 40, 45, 50, 55, 60, 65, 70.
- Garnet: weapon (+% crit damage): 50, 65, 80, 90, 100, 110, 120, 130, 140, 150. armour (+% life): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
- Citrine: weapon (+% magic find): 10, 12, 13, 14, 15, 16, 17, 18, 19, 20. armour (+% gold find): 10, 13, 16, 18, 20, 22, 24, 26, 28, 30.
- Chrysolite: weapon (+ damage, 2x for 2H weapons): 10, 15, 20, 25, 30, 34, 38, 42, 46, 50. body armour (-DFE): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

Gem upgrade cost:
- 3x tier 1 -> 1x tier 2: 125 gold
- 3x tier 2 -> 1x tier 3: 1000 gold
- 3x tier 3 -> 1x tier 4: 3375 gold
- 3x tier 4 -> 1x tier 5: 8000 gold
- 3x tier 5 -> 1x tier 6: 15625 gold
- 3x tier 6 -> 1x tier 7: 27000 gold
- 3x tier 7 -> 1x tier 8: 42875 gold
- 3x tier 8 -> 1x tier 9: 64000 gold
- 3x tier 9 -> 1x tier 10: 91125 gold