I studied fashion design ages ago, do lots of arty projects and make cushions/curtains for our home, but I still struggle to feel content with how a room looks. So I can quite easily see how hard it is for someone who doesn't have an artistic leaning to start, let alone pull off a completely curated, beautifully designed home (you're definitely not boring @NeverMindMee - we just aren't all the same 💐)
I'm extremely lucky that my DH is also artistic (he worked as a designer for 20+ years) and - mostly! - likes the same stuff as me. We've never owned a new build, have always bought period houses that have been real projects, and have been collecting 'stuff' for years, so always have a head start when it comes to decorating and furnishing a new-to-us home.
But you have to start somewhere - for us, it was car boot sales/fleamarkets, then eBay. More recently, having downsized from a 400+ year old house to a Georgian cottage in a more populated area, we've rediscovered antique auctions and fairs. In fact, I've had to reign DH in as he comes back most weekends with more treasures (books, art, decorative bits 😉) that we no longer really have space for!
I usually decide on the colour scheme (no white or neutrals for us - but there's nothing wrong with those if they sing to you) for a room - inspiration taken from a rug or fabric and DH hasn't challenged my choices...yet! I tend to buy remnants of designer fabrics for cushions plus we have lots of antique Persian rugs and kilims. But our eclectic collection of art/objects comprise all colours/styles, so, theoretically at least it's a moveable feast and I regularly 'shop my home' by swapping stuff about.
For many years we collected Art Nouveau and Arts & Crafts Movement furniture etc, but in the past few years (a result of downsizing drastically and having to offload tons), our tastes have evolved, which I've actually found really liberating!
Lamps, art, textiles, plants make a massive difference to a space and help inject character and personality. But my one abiding rule is to buy what you love - someone more knowledgeable than me once said if you buy stuff you love, however disparate, it should all work together 😁