Gold generals have 4 specialties, purple have 3; unlocked at general Lv25 (start value 0). Each slot needs a specific runestone: 1=Leadership, 2=Military, 3=Glory, 4=Immortal (purple lacks slot 4). Five levels Green/Blue/Purple/Orange/Gold. Per-step cost (runestones / gems): Green 200/4,000; Blue 500/10,000; Purple 1,000/19,980; Orange 3,000/60,000; Gold 8,000/160,000. Maxing all 4 = 50,800 runestones + ~1,015,920 gems. Runestone-chest drop odds: Leadership ~34%, Military ~32%, Glory ~24%, Immortal ~10% (Immortal is the slot-4 bottleneck). Cost tracks: pure pay ~$6,350; Shopping-Spree route ~$1,600 over ~19 months; F2P ~32 months (2-3 years). Advice: pour runestones into ONE general first; the 4th specialty is for heavy payers and only unlocks after the first 3 are all gold. Flexible (5th) Specialty: 10 types, unlocks when the 3 left specialties are gold, levels to 220, 6 qualities (green->red); 'Battle-Tested' is the F2P-friendly one; e.g. Piercing Arrows at MAX = +95% Ranged HP/Def and +140% Ranged Attack.
Original research source: Evony Guide Wiki