Aelita's Emerald and Nulgath Shaped Chocolate is bought in shops so you don't need any advice with them.
The Emerald is a 0AC misc so you can't use buy-back but it's free anyway so whatevs.
You should know right now that you can't stack shop items so don't complain.
Tainted Gem is easy. Just do Cube Reagent and stack Cubes dropped from sneevils in /boxes then go to /mountfrost and kill the 4 snow golems.
Essence of Nulgath are just drops from Makais in /tercessuinotlim.
Emblem of Nulgath requires you to have Nation Round 4 medal and it stacks to 100.
Archfiends Favor stacks to 5k and it drops from all monsters in /evilwarnul. You should know about this if you bothered farming for AFDL.