When you get new spirits, check their link runes. Place spirits with the same link rune together to activate its effect. For your support run, especially early in the game when you’re still learning, choose Thalia for healing.
Egglia uses five attributes for affinities: shadow, fire, light, water, wind. Shadow and light are vulnerable to each other. Wind is vulnerable to fire, fire is vulnerable to water, and water is vulnerable to wind. Choose assault runes that work best against the more powerful enemies in each area.