For damage increases
You can maintain Elements of Rage by fully attuning to an element (requires *either* attuning to the same element twice, or using Unravel)
Relic of Fireworks is really nice for damage as well, so if you're using that make sure you maintain both Elements of Rage & Relic of Fireworks.
Manage Weave Self & it's duration wisely. If you attune to air during Weave Self it gives you +10% damage. Weave Self lasts for 20 seconds and if you attune to all 4 elements during it, you get Perfect Weave for 10 seconds. Try to maximize your uptime of the damage bonus ^^
While attuned to Air, If you use Primordial Stance or Glyph of Elemental Power, you will apply Vulnerability to enemies.
For combos
Fire 2, 4, & Fire/Earth 3 are fire fields, Water 4 is a frost field, Water/Water 3 & 5 are water fields, Air 5 is a lightning field.
Water 2, Earth 2, & Earth/Earth 3's transmute are blast finishers. Earth 1 & 5 is a projectile finisher.
For damage
Fire 1 & 5, Water 2, Air 2, Earth 5, and most of your Dual Attacks
For defense
Fire 4 is an evade, Water 5, Water/Water 3, & Fire/Water 3 is healing, Water 4 is a frost aura, Air 3 is a knockback, Air 5 is a stun, Earth/Earth 3 is a magnetic aura, Earth 4 is uncrossable, and there's more.
Read what each ability does, and play around with them to get a feel for what you can and can't do. Get a good feel for attuning to an element at the same time you're casting an ability.
I hope this helps 👍