Congratz! You just hit 70 on your first seasonal Necromancer, now what? Before sets and at lower difficulties pets are extremely powerful and it also get you into the mind set of using pets since the Season 11 Haedrig's Gift is the Bones of Rathma set which is the pet set.
This build isn't meant to take you much further than your first few hours at level 70, it's goal is just to get you by and finish up the first four chapters of your Season Journey.
Once you get your first two pieces of the set, feel free to replace Grim Scythe with Army of the Dead, as your minions should skill enough enemies to allow Devour to replenish all the Essence you need for the early levels. Once you've got your full 6-piece set you can continue to use this build if you wish, but it's not meant to push you much further than these very early stages.