EA's idea of goth is one black dress and the Goth family. If your sim's whole personality is dark eyeliner, silver jewelry, and a wardrobe with no colors in it, base-game CAS runs out of options in about ninety seconds. The community's alt scene, on the other hand, has been dressing goth sims properly for a decade.
This collection rounds up 150+ goth picks across the full look: black-heavy clothing from fishnets to platform boots, dramatic makeup (dark lips, heavy liner, pale skin overlays), alt hairstyles, chokers and silver jewelry, and the darker build/buy pieces — candelabras, ouija coffee tables, the works — that turn a build from "modern farmhouse" into something with actual atmosphere.
Goth CC overlaps heavily with the tattoo and skin-detail categories, so if you're building a full alt sim, hit those collections next. Everything here is filtered to Sims 4, link-checked, and SFW.