Udated Build guide: Gemling Sniper commander

Edit: I just did some more elaborate explenation so figured I might as well add that info.

Just felt like sharing my current build after some discussions and idea's on discord.

The build performs really well and at all budget levels.
I think it's overlooked as most people tried to scale off on the auto-attacks instead of focusing purely on the gas explosions. Between those two ways the dps difference is immeasurable.

TLDR - video here: https://www.youtube.com/watch?v=Hh_vaaH0tJI
Updates since video: I swapped around my gear a bit to now have over 5100mana and 650 regen per second. Got 1 more gem level, lowered cast speed from 0.71sec per cast to 0.59 sec. Run 12 snipers now, and I use the new support for command skills instead of the +minion level one which increased DPS by a ton.

I noticed some people liked the idea of having a Gemling Legionnaire build that uses minions but felt like the minion nodes are to far away to make it work. My way of dealing with the many travel nodes was to lean into the strength of the GL as 1 of the ascendancy's gives double attribute bonuses so stacking intelligence actually is very beneficial.

I did start out minions but I did struggle a bit around end of act 2 and the start of act 3. I was just spamming some random minions and was still finding my jam. That was until I started using the "Command: Gas Cloud" skill of the snipers as my primary way of dps.
One of my friends started from lvl 4 with the snipers and he's having a blast however so I can confirm it works at lower levels as well.

Now I've built around that skill for damage and I use mana+int stacking combined with Mind Over Matter to stay alive.

The tree is focused on generic minion defenses/offense, mana regeneration, and intelligence nodes. I also snuck in some cast speed to get to around 70% in total to make the command skill quicker.

Early levels you do run into the issue of the command skill being quite a long cooldown and you only being able to run 1 sniper or maybe 2. They still deal a lot of damage though.
Early levels your main focus is getting as much spirit as you can and more gem levels so you can run more snipers. Gem levels decrease their reservation cost. You can also improve gem quality to further lower the cost so your first gemcutters should defenitly go there.

The build is fairly simple in gearing and talent progression.
At the start there is only 1 way you can go with talents: up.
Until you reach the first minion wheel on the tree, the circle.
I got all of those talents.

From there I went to Eldritch Battery after which I had enough mana and regeneration to feel comfortable swapping to Mind over Matter. This does depend on gear and preference a bit so you'll have to see for yourself when the turnover point to MOM is right for you but luckily the passive tree is already connected to it so it's just 1 point you can easily toggle.

After that I got some minion (fire) resistance nodes and some minion regeneration, just enough to stop the skeletal warriors from dieying to the infernal legion support.

From there I just with whatever felt best at the moment. Feel like regen is a bit low? get that first, feel bad about not 1shotting a boss? get some more dmg, etc.

When it comes down to gear obviously gem levels are the number 1 way to scale minion damage.

In short:
Want damage? -> Gem levels (scepters, chest, or amulet and possibly focus)
Want more "life" -> Mana + intelligence + energy shield (all gear except belt)
Want more mana regeneration? -> Mana regeneration (rings, amulet, focus)
Want more minions? -> Spirit (scepter, amulet, body armour)

It's as easy as that. It doesn't matter which piece of gear your specific stats come from in general so if you are looking to increase something or upgrade especially the spirit can come from any of the items.

The most important thing is to stack as much mana as you can through mana,int, and if possible ES.
You also must have resistance.
Belts in specific can't roll intelligence and gloves don't have any particularly useful stats outside of resistances so I'd recommend using the 2 of those to get as much resistance as you can so that you don't need as much resistance on other gear.

Boots the mandatory movement speed and then mana + 1 resistance roll and intellect if possible.

On the amulet you can get a % increased mana roll so try to get that if you can. If it's to expensive just a normal mana+int amulet will do. You can also get mana recoup on amulets which is nice. I didn't go for gem levels but it is possible to get a amulet that has it all. I don't even want to know the price for those though. You could also get some spirit instead to run some more minions. Maybe you can find some fun combinations/reasons to mix in some other minions as well.

On the body armour I tried to get as much energy shield as possible and like with all other items again, mana.
I also got spirit on there to be able to run enough snipers in order not to hit the command cooldown limit.

On the rings once again, mana + int, and this time also some cast speed.
Cast speed increases how fast you cast the command and faster commands means faster damage.

Also try to get high rolls for mana regeneration rate. Even a little helps a lot with sustain. With mana regeneration you want to at least regenerate more than you spend otherwise it will feel bad.

The only somewhat tricky interaction is the balance of cast speed and minion cooldowns.
Each minion has it's own individual cooldown so when you use your command skill 1 of them uses a cooldown. The pool of uses is equal to your number of minions. The faster you cast the faster you can deplete your CD's
Here you don't need 15 cooldowns(snipers) if your cast speed at full blast only can consume up to 8 for example. So in that case you could just run 8 snipers instead and use the spirit elsewhere or drop it from your gear. However if you increase your cast speed you might be able to use 9 or 10 cooldowns before you hit your cap so in that case you can increase your minions to that number.
You'll know when you hit your cap when you notice charges going to 0 and you having to wait. The ideal spot would be to see charges deplete and instantly go back to 1 again.

Updated the post to include thoughs and tips on gear progression and talent progression so it's now more usable as a guide instead of being just a showcase.

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Question has been answered but for extra clarity:

This build uses the keystone "Mind over Matter" to take all damage from mana before life. This means life won't be hit before mana runs out.
This is why we can safely take Chaos inoculation which reduces life to 1 but makes us immune to chaos damage. We can also safely use Eldritch battery to convert the (base) energy shield to mana.

Good if a bit basic build but your explanations are commendable as they can be understood by newcomers.

However you should also note that Mana Siphoning Rares are your insta-death.

Siphoning mobs are indeed a bit annoying but they are not per definition instant death.

Many people don't seem to know that only the blue ring itself drains the mana so you can actually stand inside of the circle without taking damage.

Most cases though you see them coming so you can just delete them before they reach you.

The most dangerous encounters are those where there are a lot of physical projectile mobs hiding behind a door waiting for you to open it and then blast a gazillion needles in your face or properly boosted bosses that deal a lot of physical damage.

On the next iteration of the build especially that physical damage is something I will try to get at least some mitigation to.

And indeed it's a bit of a simple build as it's just more all the answers of Q&A blended to a short story but honestly, mechanically, gemwise, gearwise, and item wise it's a very easy build so in fact it is a nice build for both beginners and experienced players.