I agree that taking elements that you like from different places is a great idea.
I would suggest a “mood board”, full of colours and stuff that appeal to you, to see how it all gels. Part of this could be online, capturing ideas.
Also, places like Pinterest will give names to various styles and types of decor, so you may find one that speaks to you.
If you're already discarding beige and magnolia, carpet and walls, but keeping the grey sofa, that's your first clue.
What sort of grey is it? What colours might go best with it?
You could look at various toning lighter and darker greys, then see if going towards warmer or colder colours harmonises best.
A colour wheel would be useful here, to look at the contrast of the opposite side of the wheel, along with the more harmonious colours nearby, or a third of the way round the wheel.
My favourite colour with (the right kind of) grey is a deep aubergine. Because I like Dark Academia, that's a colour I would have on the walls, but others may prefer to have white or pale grey walls spots of intense colour, curtains cushions and rugs, for example.