The Summoner Necromancer focuses on the Summoning Tree, but you’ll also be spending some points in the Poison and Bone and Curse Trees. Necromancer Build Guide Skills | Summoner Necro
Make sure to get a low roll when you are starting off and then upgrade it when you have enough money. Perfect rolled ones are very expensive, but you can get bad rolled ones for very affordable prices. If you don’t have a Hellfire Torch or an Annihilus yet, I strongly recommend that you get them as soon as you can. The additional passive resistances will also allow you to depend less on +All Resistances equipment, opening up more options. Having both in your inventory will save you between 20 and 40 stats points that you can spend into Vitality greatly increasing your health pool. These unique charms provide between +10-20 to all Attributes and +10-20 to all Elemental Resistances. Having a Hellfire Torch and an Annihilus will greatly reduce your stat investment into Strength.