Link's current Maximum Mana limit was 99.1 points. When a Magician's Mana was full, his body would glow with an aura and his eyes would look bright. These were simply the effects of magic. But right now, Link's Mana was down to 9 points, and so the magic aura around his body dimmed drastically, and his eyes were now noticeably dulled.
When the three mercenaries first met Link, this unremarkable looking appearance was exactly what they saw.
Link considered Lucy and Gildern's vow of loyalty towards him and decided to accept them. The three members were all equally important to the Flamingo Band of Mercenaries and Lucy and Gildern both showed promising talents and had proven themselves to be reliable comrades in battles. So Link nodded in agreement.