|Oscar has some pretty good natural skills, so this build is for players on a budget, not requiring as many skills from other units.
He comes with the Sapphire Lance+ by default, which gives him a heightened advantage against red units. This allows him to take out Red Swords more easily as well as withstand red mages better. He would be far more vulnerable to green units however, so he should take caution around them.
His Assists are either Reposition or Rally Spd/Def. Reposition is a good, versatile Assist that can help Oscar propel his allies into the fray, or he can use it to help an ally flee from an oncoming threat. He also comes with Rally Spd/Def naturally, which grants +3 Spd and Def to any ally.
His Special is Moonbow, as it has a fast charge and a defense piercing effect, which can help Oscar break through tougher foes.
His A skill is Fury 3, which grants +3 to all stats, improving Oscar's overall combat performance. However, it injures him for 6 damage after combat, so the player would do well to keep him healthy in endurance styled maps.
His B skill is Lancebreaker 3, which he comes with naturally. With his weapon already giving him a heightened advantage against swords, this skill covers opposing lancers, as Lancebreaker denies them the chance to do a double attack while guaranteeing Oscar to perform a double attack against them.
Oscar's C skill can be Spur Spd/Def 2, which he comes with naturally. It grants +3 Spd and Def to any ally adjacent to him. When combined with his Rally Spd/Def, he can help grant +6 Spd and Def to his allies, which can help Oscar be a team player no matter what kind of team he's on. However, he can use other C skills, like cavalry buffs if he's on a full cavalry team, making his C skill slot flexible.