There are many endgame setups in Diablo 2 Resurrected Ladder, and with the Sundering Charms added in Ladder Season 2, some of the builds have shifted. More unique builds have become possible, while some builds remained strong or have become even stronger. Here is the endgame for the Frost Nova Sorceress.
Basically, the Frost Nova build requires at least 92 skill points, so you'll be done by Lv 80. However, it's not over, as you'll need to distribute additional skill points on Cold Mastery depending on how many additional skills you have from your equipment. If you've made -195% to enemy cold resistance, use your remaining skill points on Energy Shield or Warmth. The reason you master Telekinesis is that it's a valuable synergy skill for the Energy Shield.
Energy Shield is a unique skill in Diablo 2. When the Energy Shield is activated, all damage is filtered through your mana. Some damage will be absorbed, and only a portion of the damage will affect your health. This is a great advantage for the Sorceress as she isn't as tanky as other characters, but the biggest advantage of the Energy Shield is that you don't need to think about all the resist stats. The only resist stat that matters is Poison Resist, which drains your HP slowly.
Helm: Nightwing's Veil / Harlequin Crest
Weapon: Death Fathom / Heart of the Oak (KoVexPulThul) / Doom (HelOhmLumLoCham)
Shield: Spirit (TalThulOrtAmn)
Armor: Chains of Honor (DolUmBerIst) / Skin of the Vipermagi / Ormus'Robe
Gloves: Magefist / Trang-Oul's Claws / Frostburn
Belt: Arachnid Mesh / Snowclash
Boots: War Traveler / Rare resist boots w/ poison length reduction
Amulet: Mara's Kaleidoscope / Magic +3 Cold skill+FCR(+10%) amulet / Crafted FCR(+20%) +2 skill amulet
Rings: Stone of Jordan / Bul-Kathos' Wedding Band / Rare FCR ring
Swap: Call to Arms (AmnRalMalIstOhm) & Spirit (TalThulOrtAmn)
Cold spell Sorceresses share the same equipment build, as their goal is to maximize the damage of their spells. As the Cold Mastery skill reduces enemy cold resistances, it goes perfectly with the Sundered Charm: Cold Rupture. Due to Cold Mastery and Cold Rupture, the build is powerful even without the aforementioned equipment, but it is quite expensive to set up the endgame builds as the D2R Ladder Items supply doesn't meet the demand.
All stats should go to Energy as long as you can wear all the equipment. Since you'll need to equip the Spirit Monarch on your off-hand, you'll need 156 Strength, including all the additional stats from Hellfire Torch, Annihilus, and other equipment. You can invest some stats on Vitality for more stability, but keep it to a minimum.
Act 2 Holy Freeze / Prayer
Helm: Andariel's Visage / Tal Rasha's Horadric Crest / Vampire Gaze / Crown of Thieves
Armor: Fortitude (ElSolDolLo) / Treachery (ShaelThulLem) / Gloom (FalUmPul)
Weapon: Insight (RalTirTalSol on Polearm)
There are several choices for the helms and armors, but Andariel's Visage and Fortitude should always be your no.1 choice. The additional attack speed and life steal from Andariel's Visage, and the enhanced damage from Fortitude is too big to ignore. Make sure you make a socket on Andariel's Visage to equip a Ral rune or a jewel with +30% fire resist and 15% attack speed to make up for the -30% fire resist.