Build an opening repertoire is hard and may take a few years to have a real solid repertoire. I personally don't study the opening, in my level I can make the moves, but without understand they perfectly. The sicilian has a lot of theory, so I suggest you to study the kan or palsen sicilians wich has less theory. When I studyed the english my problem was with the transpositions, who happened a lot in my games.
In general, 1800- players will not play the lines in book, and your study will be "useless".
Good luck! Sorry for the bad english
When I was a child and first learnt to play chess, I exclusively played the Guico Piano, which everyone seems to now think is a bit rubbish. I'd love to do other stuff, but just feel that learning umpteen variations is too much hard work. Is there any sense to learning the English and the Sicilian so that I can adopt a similar system whatever side I'm playing? If so, I'd love a few pointers on these. If not, can people suggest openings for either colour that aren't too theory-heavy and lead to middlegames with some attacking chances but don't compromise king safety too much? I appreciate that's a big ask, but you all seem such lovely people.