Example Gear
Above you will find example gear that caps all resistances (including chaos), takes care of all attribute needs, gives you full ailment immunity and over 15 million single target dps. This is just an example to show, how you can build your character. You don't need to get all of the same modifiers, but it gives you an idea of what items might be good in each slot.
Cooldown Reduction
In your 
Stygian Vise or Passive Tree, you want to use one Abyss Jewel with at least 2% Cooldown Recovery Rate. This will make your mines detonate faster due to the internal cooldown of 
Detonate Mines gem.
Improving Damage
One of the easiest ways to improve your damage is to incorporate the following unique items into your build:
- 
The Arkhon's Tools extremely strong and useful belt. You will have to go back to using skitterbots, and make sure that you are ailment immune, in order to avoid the downside. It's also possible to get shock immunity from something like 
Tempest Shield, overcap your resistances for scorch and reverse the chill effect with 
Winterweave. If you combine it with 
Bonechill Support in your skitterbots, you will also take less cold damage based on the chill effect on you. This however is not very consistent in terms of uptime. The skitterbots don't always follow you, and I would only use the reverse chill tech if I wanted to 100% focus on bossing. Either way you should definitely be using this belt.
- 
Heatshiver this build can freeze pinnacle bosses, which makes Heatshiver a very good option.
- Foulborn 
Tulborn with +3 to Level of all Cold Spell Skill Gems will give you more damage than most weapons you can get early on.
- 
Carcass Jack or 
The Restless Ward with +2 to level of Socketed AoE skills and/or +1 to level of all Socketed Skills will massively boost your damage. This is a good option early on, if you can get it.
Improving Defense
Your defense will scale with your gear. The more Life, Resistances, Evasion and Energy Shield you get, the tankier you will get. At higher budget, items like 
Progenesis can vastly improve your survivability.
If you want to improve your defense, there are a couple of ways you can go about it.
Spell Suppression - you can get Spell Suppression on your gear, and pick up the 
Instinct and potentially 
Inveterate notables. Pathing down to Inveterate, would allow you to also grab the Frenzy charge notable nearby and anoint 
Savagery instead.
Block and Spell Block - you can also lean into block instead. Get as much block as you can on your shield and pick up 
Arcane Sanctuary notable. You can get more block from cluster jewels, shield and body armour modifiers, 
Rumi's Concoction, 
Replica Reckless Defence and eventually you can opt to use 
Svalinn
Witch
Elementalist
