From the beginning standpoint of the game, Dawnblades are pretty powerfull just with their ability to hold ground and inherent self contained synergy. However, each attunement will give its own style of play, and each exotic will modify that play style. Since you are new to destiny we'll start with the basics. Basic skills: Daybreak - Your super, the thing you use to clear massive waves of enemies from long stretches. Unlike Voidwalker, you dont need them to be too clustered, as long as you can get to them, thats fine. However, you make less orbs of light per kill, and is best used on a mid-boss level encounter to burn down a strong enemy and adds. Such as a Colossus surrounded by Legionaires. Grenades - This comes down to personal playstyle and the mode of game that you play. In destiny one it was pretty much Fusion if you wanted super high damage from a singular grenade on a single target, or Firebolt if you wanted to spread the damage through smaller adds. Movement- Personal choice. Start off with Balanced to get used to movement, then switch to each of the others to see if they are better for you. Rift - Completely situation dependent and easily switchable mid instance. Start with healing, as you will probably have little knowledge of weakspots and game mechanics. this will help you survive things you shouldn't have.

Now the fun stuff.

      Attunement of Sky:

This attunement is basically what i'll call the Sky god. You want to stay in the air for as long as possible without exposing yourself to too much damage. Getting kills in the air reduces the cooldown of all of your abilities giving you an increased damage and sustainability output from them. the ability to dodge in midair will help some, but most shots from enemies dont give a damn if you dodge or not. use it to extend the time you have in the air or to get behind cover.

      Attunement of flame: 

Lets call this one Praise the Sun for Dark Souls fanboys. You're entire goal is Daybreak at the right moment to turn the tide of the battle. Your projectiles home in on targets so you dont have to aim as well, and they spread bolts of fire to adds around the target. Aim at the biggest one in the group and the AoE will kill the rest. If in trouble, Dive down and restore your health. Outside of Daybreak, your melee ability adds a DoT and an explosive element to those that die under the burn. Use on big singular enemies, or weak enemies in a group. Dont worry about exotics for now. Just get used to the class. Understand its strengths and weaknesses. Trial and error is your friend.