D2R Newb returning - Nightmare HC Firetrap

Hi Everyone. I haven't played D2R since launch, where I got my non-ladder warcry barbarian to level 75 in hell solo before I burnt out in act 5.

I came back last week with my RL friend and i started playing an easy beginner guide for a class I've never played, the assassin.
I am using a wowhead beginner guide this one: https://www.wowhead.com/diablo-2/guide/ ... strategies

This basically walks me through what to do 1-40.

I want to dive a bit deeper but I tend to get overwhelmed and frustrated with the amount of choice in runewords and builds. I tend to like the game of D2R but I am not huge on theorycrafting or knowing "when" to switch a build because I am fairly casual. Is there a good set of goals for me to prepare for level 40 when this guide recommends respeccing? The only plan I have right now is to farm for Spirit runes and then do the cow level to try to get a crystal 3 socket sword that I can add socket to. Beyond that using the ancients pledge shield is all I've really planned for. I have had fun with this fire trapper but know it falls off because of resistance to fire.

Any tips/tricks and uniques/item merchant farming i should do will be greatly appreciated. I am currently running Stealth/Leaf and no other rune words, and have a teleportation staff i grabbed from merchant for 16k.

This is in hardcore mode at nightmare difficulty act 1 currently.

Spirit, Lore, Ancient's Pledge and Insight (for Merc) have runes easy to farm on

The Countess nightmare

(you can farm a Spirit

Crystal Sword base on Normal Cows )

Fire trapsin is nice until around A4 NM when the first regular fire immunes start to appear and your damage output falls behind, as you mentioned.
Would recommend to get an

Um rune and a 3 socket

Phase Blade somehow, build

Crescent Moon and switch to

Lightning Sentry and

Death Sentry.
Do not use

Crystal Sword or

Dimensional Blade as trap cast speed depends on weapon speed.
Also put one point in

Mind Blast as this enables you to farm cows in a save way by converting one or two, wait until two or three others die by your traps and elimante whole screens with

Death Sentry.
Also mind that in HC you prefer maxed resists and physical damage reduction over damage, even when playing a "saver" build like trapsin.
My number one farming spot for any trapsin is cow on any difficulty. This ladder season i played trapsin a lot and farmed 95% of my time in hell cow until level 91