tbh, I get the feeling you won't "level" in to stat in this game. I'm guessing it'll be more like this;
Glad goes out to solo. He'll have a Sword skill, a Shield skill, a Defense skill, an Evasion skill and some other skills likely.
When he goes out to solo, attacking mobs grants "experience points" towards his Sword skill. Higher Sword Skill means he gain access to better weapons, as well as increasing his potency (meaning Damage and Accuracy) with Swords. Using job abilities and spells improves their efficiency (read; they level up) to increase their potency, thus making them stronger. Once it levels up enough, you it grants you access to a new ability (Fire > Fire II > Fire III > Fire IV > Flare), assuming your Skill (for example, Fire Elemental Skill or Ice Elemental Skill) is high enough. If the Gladiator get hit, his "Defense" skill increases, giving him improved Defense, while Evasion from Evading grants him new Evasive abilities, and Shield Skill gives him decreased damage from blocking (and maybe self-heal skills and Enmity Increasing skills?).
I'm also venturing a guess that stats are obtained through certain Guildleves, and not through leveling your character.