I recently finished uploading my final video in a series, where I complete Spirit Slayer on all of my 18 characters.
Every class combo is there, Magicka and Stamina. Some are done twice, since I have 3 characters of each class, so there's 2 magplar, 2 stamblade, 2 stam dk, 2 magcro, 2 magsorc and 2 magden.
The builds for all the Stamina runs, and all the Magicka runs, are pretty much the same. If my character was already using Shadow mundus, i didn't bother changing, but if it was atronach or something, I switched to Lover. Champion points I used the tool on ESO-U.com.
1 Monster helm (something with Weapon Damage, Weapon Crit, Physical Penetration or Max Stamina)
1 Pale Order ring
5 Vicious Ophidian (2h sword or axe frontbar, necklace, ring, shoulder)
5 Two-Fanged Serpent (5 body pieces)
Maelstrom Bow backbar
Brawler and rearming trap front bar, endless hail backbar, then fill in the gaps with whatever
1 Monster helm (something with Spell Damage, Spell Crit, Spell Penetration, or Max Magicka)
1 Pale order ring
5 False God (Necklace, ring, shoulder, and another body piece)
5 Mother's sorrow (inferno staff, and the remaining 3 body pieces)
Maelstrom inferno staff
Most magicka classes already have some built in healing/survivability, like puncturing sweeps, swallow soul, burning embers etc. If you're worried though, you can always put harness magicka on too
If you're on a Stamina character, you're going to want to do the Blue portal first, then go into the Red one and pick up the Health buffs, then go into the Green one and pick up the Stamina buffs.
For Magicka, you start with Green, then go Blue for Magicka buffs, and Red for Health buffs.
By doing it this way, I found it not too difficult to get the Spirit Slayer (though i must say, i do have a lot of PvE experience).
With the additional health and stamina/magicka, it made things feel a lot safer.
I hope these videos help you, and don't hesitate to ask any questions, either here or in the YouTube comments!