Useful things

A small tool for measuring seam allowances and hems. I also have the inch version and use 1/4" for a 7 mm seam allowance, as this measurement is missing on the cm version.

This fabric marking pen is like writing with a ballpoint pen, but the ink is heat-erasable.

Having a pair of thread snips by the machine is a must-have. This plier-style variant is both sharp and quick to use. I also use it for clipping corners and making notches/markings on the fabric.

Some form of elastic threader is a must for threading elastic and drawstrings through casings.

If you are sewing your own cords/drawstrings and straps, a loop turner is a must-have. It easily turns your fabric tube/channel right side out using a small hook at the end.

A glue stick or glue pen for fabric is very useful on many occasions. Primarily for using as an 'extra pin' when sewing slippery or flimsy fabrics.

There are many different variations you can use; non-woven, construction plastic sheeting, paper pattern paper, and personally, I use parchment paper most of the time.

Regular hand sewing needles are a must-have even if you own a sewing machine. You may need to sew closed turning holes, attach buttons, etc. A kit with assorted sizes is perfect for your sewing box.

This is probably the presser foot I use the most after the universal foot.
This one makes your zigzag or overcast stitch over the edge of your fabric without pulling the fabric together. If you don't have an overlock machine, this one is a must.

Sometimes you sew in fabrics that tend to shift or where the metal foot likes to hold on to the fabric. Then this teflon foot is great! It is especially useful if you are sewing in leather, foam, plastic, etc.

An adjustable stitch guide presser foot is very useful when sewing hems and topstitching to get an even distance between the fabric edge and the seam.