Best place to buy varies a lot. I have gotten awesome sheets from wild places so let's start with some basics. Microfiber is an affordable option, it's made of polyester (so not fantastic for the environment) but it's soft and less prone to pilling than other fabric. But it isn't breathable and it's fantastic for sensitive skin. Cotton Jersey is nice to sleep on, breathable and affordable, it's kinda like sleeping on a bunch of soft t shirts. It's knit. Neither of those though sleep super cool though so if like the refreshing coolness you are probably better off with woven cotton. (Fun fact: if you wake up from a nightmare and can flip over your pillow or have a cool one to use you won't plunge back into your nightmare when you fall back asleep) Cotton okay so lottttsss of info Most lauded kinds are the ones made of long-staple fibers like Egyptian, pima, Supima® but they aren't the only types of cotton in the game so they aren't the end all be all. Thread count. The number of vertical and horizontal threads in a square inch. Good sheets are usually between 300-800 count generally higher threads means it will wear well and perhaps even soften with age, and the sheets will be softer in general. But although you can get higher thread count sheets you might be paying for bubkis some of the brands artificially inflate the thread count (using yarns that are actually spun together and counting them as separate) that ultimately detract from the quality. And I have some great sheets that 200 count but are finished beautifully and thus are awesome. Other words you may or may not see Sateen - has a satin weave so it's nice and soft but not as durable they feel luxurious though Percale - crisp feeling and at least 180 thread count, durable, crisp, plain and unfussy Combed cotton - they combed the shorter fibers out. It's soft and strong

If I were you I would wait until black Friday so you can get some great deals, but make sure to only buy products the stores normally have on hand, if you buy something made for black Friday it's crap. I always wait unless I'm desperate (a former roommate spilling hot cooking oil into the linen cupboard) I would also only invest in a nice set if you have a bed you are going to have for a long time. If you think you might upgrade the size of your bed wait to get a few sets to go with that.

For blankets I only use feather down duvets and then change the covers out to whatever the heck I want (usually white or plant prints or green) get some different weight ones like summer (thinner or less) and winter (thicker or more) for different seasons and temperature. But depending on how you sleep you might want one over the other all year round. Other blankets I use are my weighted one (for the love of God buy one you can clean) and a random one I've had since childhood that's woven cotton from Walmart, and family quilts. I suggest buying a white duvet or duvet insert, because then if you have a light colored cover it doesn't show (curse younger me and my obsession with dark gray). Also think of your life style, I have always bought duvets a size bigger than my bed because I'm a blanket hog and want to become a burrito at night. This does look silly if I make my bed the traditional way so I as a rule don't, I trifold them at the base and then yeet them up to me when I crawl in. King size blankets are really cozy. If you are also a blanket hog too or just like to not fight with a partner or are less into cozy I would suggest two twin size duvets with matching or coordinating covers, no fighting over blankets and it looks cool.

Also upgrade your pillows at this time too! Then mark your calendar so you can wash them every three months and replace them in 2ish years! I have a lot of pricey pillows so I rotate them (stretch your neck my human it'll save you) but standard pillows super need to be cleaned to stay nice.

TLDR There is googleable vocab, and lots of personal anecdotes so if this wall of words is too much, know what you like for sleeping preferences and touch fabrics to see if you'll like them.