Ok this is my i haven't seen a new build for a v1.13 Summon Necro so I'm going to make one and keep it short and simple. There are basically 3 ways to go with this build and I'll explain them as I go through the guide. I'll also go over a few of my strategies with playing as a Summon Necro.
Strength- None, do NOT put any points in here. Collect str charms, items, rings, whatever you need in order to reach your strength requirements for your armor and then you should be good. Also keep in mind if you are getting a torch and anni, that will be another 30-40 str points Points into strength is a waste of valuable life points.
Dexterity- If we arent putting any points into strength there is no reason to put any in here. You are not going to be running into the battle, you have minions and spells to take care of that.
Vitality- Every point from every level you get should go right into here. You will need the life desperately if yuo plan on running ubers solo or bosses, just in case you get hit it helps to have the life.
Energy- MANA POTS! no points here
This part is very simple but no one seems to get it right so I'll explain. Skills:
20 Raise Skeleton- Skeletons are the basis for this build, you are a summoner so it only makes sense to max this. 20 Skeleton Mastery- Might as well make your skeletons stronger, never hurts. 1 Clay Golem- Is useful because he can slow your targets giving you more time to set yourself up and start attacking. 1 Golem Mastery- Mainly used as a prerequisite for Summon Resist and it doesnt hurt to give your golem a little more power, especially after you get the bonuses from your +skill items. 1 Raise Skeletal Mage- Once again a prerequisite for Revive which is absolutely necessary for a summoner. Also, it doesnt hurt to have a little extra help especially when you get +skill items which will increase them just enough to be useful as a distraction, other than that they are pretty much useless. 1 Blood Golem- Now, this is used as a prerequisite but also with the new patch you no longer take damage from your blood golem so he is only beneficial. If you find yourself needing life just go ahead and pop out a blood golem and let him do some damage and watch your health go up. 1 Iron Golem- Another prereq but also very useful if you find the right item to make him out of. Personally I use the iron golem as my golem of choice simply because I can make him out of an insight which uses low runes and boosts my mana with the meditation aura. Doing this frees up your mercs spot so you can put a more valuable weapon on him like Infinity if you choose to put points into the poison tree. 1 Summon Resist- Will significantly increase how long your summons live because they wont take as much elemental damage, a must have. 1 Revive- Only need 1 point into this because for every point put in here you can have one more revive. With your +skills from your gear added in you should have plenty of revives by then.