Bukkit

With Item Lore Stats you can allow items with stats to upgrade as the player levels up. In the config there is a section called statValuesChangeOnLevelChange, this contains all the values required to control item upgrades. Video demonstration of a player rapidly changing level.

enabled: true

This value will enable/disable the item upgrade feature.

upgradeCap: 5

This is the amount of times an item can upgrade. If this is set to 5 it means the item can only upgrade 5 times and will not upgrade any further.

  stats:
    armour: 0.1
    dodge: 0.1
    block: 0.1
    critChance: 0.2
    critDamage: 0.3
    damage: 0.1
    health: 0.3
    healthRegen: 0.1
    lifeSteal: 0.2
    reflect: 0.1
    fire: 0.1
    ice: 0.1
    poison: 0.1
    wither: 0.1
    harming: 0.1
    blind: 0.1
    movementSpeed: 0.5
    xpMultiplier: 0.1
    pvpDamage: 0.3
    pveDamage: 0.3
    heroesMaxMana: 0.2

These are the values that each stat will upgrade by. So if you have 2.5% Armour on your helmet, the next time it upgrades it will have 2.6% Armour as the stats are round up so 2.5% + 0.6% = 2.56% and then the value is rounded up to 2.6%. Setting these values to anything less that 0.06 will prevent the stat from upgrading so make sure all stats are above that unless you specifically don't want those stats to upgrade.