To share some of the tools I found useful when sewing clothes.
Measuring tape! To measure your size and also to measure the fabric.
Pins, lots of pins to hold the pattern to the fabric and to hold fabric together when sewing. When sewing lace or tulle, you will need to use safety pins.
Pincushion or the newer magnetic pin bowls (grabbits).
Tailor's chalk or the newer water soluble marker pens.
Thread cutters, only if your sewing machine doesn't have one.
Unpicker, for all those mistakes you will be making. This tool was specifically made for this purpose and comes in really handy.
Fabric Shears, 1 for plain fabric and 1 more for sequins/beads. A scissors sharpener will come in handy for the latter.
Lotsa thread colours. I usually get 1 or 2 per sewing project and it gets used up. I do buy larger spools of white and black thread as it goes with almost everything.
Extra bobbins as the sewing machine only comes with 1 or 2 pieces. You need at least 1 bobbin per thread colour.
Sewing Machine needles. The sewing machine only comes with 1 piece that will break after a couple months of use. I get different types of needles for different fabrics, you have bigger needles for thick fabrics like denim and sharper needles for stretch fabrics, etc.
A ready stock of fasteners (hook & eye, press studs, buttons, zips). It's nice to pick out custom pieces for your sewing project, but such a nuisance when you have to make a trip to town everytime to get it.
Sewing Machine Presser Foots. Your sewing machine will come with 1 or 2 basic presser foots, you have to buy the rest separately. So far I have bought a few additional presser foots, am considering getting more but not sure if I will really use them.