Enter the Gollux map via dimensional portal or accept the gollux quest via lightbulb.
Talk to the npc to start the questline which is only a few cut-scenes. Afterwards you can then gollux!
When defeating gollux, there is a chance of equips dropping and gollux coins.
Gollux coin drops are not shared where as equip drops are shared between party members.
Gollux can be fought in Normal, Hard, and Hell.
The higher the difficulty the better the drops and the increase in coin amounts.
It is recommended to use advanced gollux scrolls for any gollux related items.