It's best to not level (Level one to high 40's/early 50's) as a pure summoner in PoE. Summons require a lot of support from the tree and gear to be able to withstand any form of punishment against bosses and act3+ mobs. At the start, you'll build a bit like a spell caster while working on the
skeleton of your build, as you move past all the summon nodes then you start taking all the minion nodes at once when you believe you're ready. Be sure to refund all the points you spent on spell damage beforehand and put them into minions but it's not really a bad idea to keep some as you'll still be supporting the frontline with stuff like traps, freeze pulse or firestorm.
Nowadays, there are a lot of different summoner types, ranging from animating weapons, zombies, raging spirits(Think bone spirit build) to the new element golem skills and even supporting auras thanks to the generosity support gem. Some of these skills don't use or require all of the minion nodes so you are free to take a lot of other things in these types of builds. Summoners also have new buffs that can make corpses/consume them and also a recall-type spell to heal your horde while also protecting them from harmful AoEs.
Summoners aren't as good as they once were back when they got all their new bells and whistles, but as long as you don't focus on being only a summoner at the start, you'll be fine in the later levels once you fully transition over to one, even if you don't have all the best gear at the time.