The core cards for the decks are all of the Evil Eye cards and the rest being tech cards. As for extra deck it's the same evil eye monsters being core rest are just there for tech and stuff. You should always try to bring out your link 2 monster or if you can link 3 monster evil eye monster since their cost for activating effect only applies to monster on your link zones so if you don't have any monsters on those zones its just 500 atk buff.
So, as for the combo it's simple you want to have serziel or the field spell so we can search serziel or basilius on our starting hand while serziel being the best, we play 3 of evil eye of selene so we don't have to search it often also, we want to have some extra any evil eye cards for the combo.
The combo is you summon serziel you search for basilius if you don't have it but if you do add evil eye of reemergance to go into link 3 if you also have evil eye selene, then use basilius effect to send eye of gorgoneio to grave then use gorgoneio effect to discard any evil eye card the add any evil eye card you need based on what you have and what you want. Then link summon evil eye empress or ruler of evil eye if you have reemergance then equip evil eye selene.