In the great scheme of things it doesnt - and pegs on the corners really help me :)
I think my superkingsize duvet was around £40 in the sales and duvet sets are pretty cheap.
I always buy for my bed, the best I can afford. The first lot I bought back when dh and I got our first kingsize bed back in 2001 - I paid £100 a set - in the sales - I bought two - one is still being used
I love my cotton sheets and buy the highest thread count I can afford - in the sales.. Using a top sheet places less wear on the cover, less chance of sweat stains etc
I appreciate that money is tight - it is for everyone, hence Im repurposing a lot of mums old fashioned furniture and the spare rooms have cheaper covers and duvets - because they dont get used daily. My own bed, is a different matter. I spent on mattress , Ive spent on sheets, but Ill use a cheap throw to tie the colour in - Like you I prefer neutral bedding - mines all cream. And yes I did once buy a very expensive duvet, then I hit the menopause, it was too hot, cost me a fortune to get dry cleaned - its away
Getting creative as best you can also helps. DH is a whizz with a staple gun and can refurbish chair seats , headboards. Material is often curtain from a charity shop. I needed tie backs for the very cheap curtains I got in the sale . they were costing the same again, Ive crocheted a couple - cost an hour of my time and possibly 50p in yarn . I bought dead cheap velvet lamp shades ( £6 each) for two ugly squat stainless steel touch lamps mum had - they look amazing now. Like you Im in the eves ( had to saw the legs of a wardrobe to get that to fit ) , and a very long room with the velux windows the far end, The wall behind the bed I papered and I use 6x4 cheap frames to mount wee art postcards on the smaller walls
My living room, again , no wall height ( same floor ) so Ive put wee narrow floating shelves to put wee bits and bobs on . Just a wee bit under the eves but deep enough to hold a picture frame or a wee ornament . It give an impression of height , gives me places to show off my bits without having to fill the room with furniture
If you are scared of colour, look at a colour wheel . You have your natural base and you have your red, look at the colours opposite the red, look at the colours either side. You start with the basic colour wheel then you dig deep with the colours, warmer, cooler, . That's all I do . Im no interior designer , I keep it plain and simple and not ageing, then add the splashes of colour