Valens is the male protagonist of the game. He is the son of the famous gladiator Munio and hails from Imperia, growing up with his childhood friend Ludo. Valens is the most well-rounded Medium Class combatant in the game with above-average Power and Initiative and exceptional Accuracy and Defense. Valens is a good choice for almost any situation, and can even pull his weight against many Heavy Class gladiators due to his Defense being greater than many Light Class gladiators.
On top of his great attributes, Valens also offers an impressive set of skills, with many useful Innate skills and some nice Attack moves. Skills such as Awareness, Indomitable Will and Discipline should be saved up for and taken early on to protect against negative status effects in battle. On top of Combo and Affinity attacks, Wide Swing is a good move when combined with Empower Self to improve accuracy because it cannot critical hit.
Shield Hit only uses 1 SP and will deal quite a bit more damage than your basic Strike, so it is a very reliable finishing move if you're all out of SP/AFF. Smack Back has a 100% chance of hitting all opponents around Valens and will actually deal considerable guaranteed damage to light gladiators, so it is worth investing in if you like to take on large groups with Valens.
Any Affinity type works well with Valens, which means you should go with Air or Earth so your third-level Affinity attacks have a good effect (Air freezes and Earth petrifies while Water only lowers Movement and Fire poisons). It is possible through a glitch to get Munio's Sword, Shield and Armor before you reach the Southern Expanse, so if you go with Air affinity you don't have to worry about not being able to damage a Dervish. This is because Munio's Sword is linked to all Affinity types.
Valens can and should be used in almost every battle that he meets the requirements to enter. After using Empower Self he is able to block or evade almost anything thrown at him. With that in mind, the best accessories for Valens are the Medal of Bravery, the Medal of Rank, and the Medal of Stature. The Medal of Bravery will allow Valens to face every attack, meaning he has a chance to block even when attacked from behind. The Medal of Rank makes surrounding allies immune to Fear, Confusion, Charm, Stun, Petrification, and Doom; this comes in handy in fights against Amazons, Berserkers, Minotaurs, and the Undead. The Medal of Stature reduces all incoming damage by half; this trumps the Iron Fist, which only reduces damage taken from critical hits. Also, the Medal of Stature (along with other damage reducing accessories) is far less expensive than most other accessories, making it viable early in the game.
Make sure you start every battle by using Empower Self, and pick on lights with Valens first since he will have a damage bonus against them. The only downside to Valens is that he lacks a long range Move-to-Attack option; this is trumped by his ability to fight once he has closed the gap however. Make as much use as you can of Wide Swing and Smack Back, keeping Valens right in the middle of the action. If you use the glitch to get Munio's Sword and armor early, your affinity should fully charge with a single hit, so be sure to get an Affinity Attack 4 to be used often.