There are certain things you'll need if you want to start sewing your own clothes or home decor. It's more flexible and less annoying for me than trying to find home decor I like or dig for some from periods I like as they are notriously scalped (especially any 60s and 70s textiles produced under former system) or clothing (vinted in my country is completely depopified). You don't need to have expensive sewing machine or anything first - if you'll feel you need a better machine or scissors after a while, go for it! It will last you long time if maintained properly.
Jump to section: sewing machines, irons and ironing boards, scissors and cutting accessories, needles, threads, marking tools, miscellaneous - pins, measuring tapes, rulers, etc
You don't really need a computerized machine. Compared to classic, simple home sewing machine they have more points of failure and will cause more issues with servicing (especially out of warranty) though they allow for more control over stitch lenght and width, have loads of decorative stitches, etc. I don't really work with modern machines currently but one thing is to avoid cheap machines - they don't last long, have plastic internals which can get crushed, etc, etc. They also often have oscillating shuttle bobbin driver, which I hate (and made me hate sewing for a long time) and it takes longer to switch the thread or thread can be caught inside of it and cause issues. Oscillating hook drivers were more commonly found in more expensive machines, but they also can be found in vintage sewing machines (like Singer 800 class and clones) and now they appear in more basic and simple machines on the market.
A basic home sewing machine should have following functions: regulation of stitch lenght and width, adjustable needle position, regulated presser foot pressure, well working bottom feed. Basic straight stitch, few varieties or zigzag stich, buttonholes (either automatic 1 step or 4 step half automatic). Overlock stitch, reinforced straight stitch, elastic stitches or blind hem stitches are helpful but not necessary. It should have metal internals, as it will last you long time.
You should have your machine serviced on regular basis - oiling and cleaning. With vintage machines it's a good idea to have it serviced first, even if it works well.
Check compatibility lists while shopping for presser foot or bobbin spools. For an example 800 class Singers use specific type of bobbin which is curved like a lens and normal bobbins won't work with it.
Most basic presser foots you'll need additionally are zipper and, invisible zipper ones. Blind hem, buttonhole and overlock foot if you have these functions in your machine. Rolled hem foot is good to have around too. It's available in various widths (3mm, 6mm).
There are different types of irons available on the market, but one you should currently have at home will be enough. It should have temperature regulation and steam generation/sprayer. Home steam irons are good too as they have bigger water containers, but usually iron itself is pretty light and there's not much of temperature regulation. It might be annoying while pressing fabrics like linen or cotton, which need high temperature and more more weight to be pressed well. There are also gravity feed irons I see used by professional dressmakers or dry cleaners, but normal home iron will be still good.
Usual ironing board will work fine for most of ironing/pressing. It should have adjustable height, as you should adjust it to your height. There are small, sleeve ironing board available which make life easier but you can press sleeve seams without it too. Another helpful item for ironing/pressing are tailor hams which are small round-ish pillows used to press darts, collars and sleeves set into armhole.
You need a two pairs of scissors. One office, paper ones for all paper patterns. Other ones, the proper fabric ones which you should only use on fabrics to keep them sharp - paper can dull them very quickly. It's good to have small, sharp scissors (like embroidery scissors) or thread snips on hand while sewing. You can get a rotary cutter and a cutting mat - but they are more expensive, though great if you sew loads of knit fabrics.
I currently use classic orange Fiskars scissors, which were more pricy but they serve me well.
Properly check needle type which your sewing machine uses. It's good to have more needles on hand in case if they will break or will become blunt. Basic set of machine needles I recommend to have on hand is 2 70 needles, around 5 80 needles (universal), 1-2 90 needles (thicker fabrics), two ball point needles for knits (if you sew them).
You'll also need a good, sharp set of hand sewing needles to finish off topstitching nicely, hand hemming with blind stitch or to sew together bits you can't sew on machine well (for example, at the end of invisible zippers).
Avoid cheap thread sets - they often aren't really strong and came on really tiny spools that don't last long. Polyester thread is most common, cotton thread is still available but it's harder to find (at least for me) and a bit less strong. There are specialist thread types like elastic ones, topstiching thread that is thicker, machine embroidery threads (which can be used for sewing delicate fabrics like chiffon). Standard 120 thread can be used for thinner fabrics if you'll lower thread tension and use thinner needle.
It's good to have few spools of while and black thread on hand. Additionally basic set of grays, beige and cream will be always used up. Bright colored threads for basting.
Most common is chalk or soap. Chalk can come in soap shaped form, in pencils or as leads (for a dedicated lead holder, I recommend Koh-I-Noor one). There are washable fabric markers available on the market, which allow for more precise marking.
White chalk will work on dark colors and medium dark ones, pink/blue is good for marking on light colors. Test it before marking if it will come off by brushing it off, with steam or water.
pins Get few sets as they will get lost constantly. They should be sharp and have glass heads. Avoid cheap pins with plastic pearl head. They will melt while ironing.
measuring tape Depends where you live, but in Europe at least they come most commonly as 150cm long a bit stretchy plastic tapes with metal bits on the end with a little holes. Replace if it will get stretched out.
rulers A long metal ruler and hard plastic triangle ruler are helpful to have around, both for copying patterns, marking things on fabric or drafting own patterns. Higher quality rulers will last you ages. There are sets of specialized patternmaking rulers which help with drawing armholes, necklines and other curvers. Worth to buy a set if you want to use your own patterns mostly.
pattern paper Semi-transparent, white A1 size paper for copying patterns from magazine pattern sheets (not applicable if you are American, unless you like yuropean pattern magazines) or transformation of basic blocks. It's easily foldable and easy to store. Basic pattern blocks should be made off thick cardstock, as they will be copied and copied all the time
next - sourcing sewing patterns