The only kitchen tool that survived my last move intact was a scale my brother left at my apartment two Christmases ago. I don't actually remember which of my two apartments I lost the last measuring cup in, just that by the time I finally tried baking cookies from scratch, the scale was all I had left.
Your first day
Pick any basic drop-cookie recipe that lists ingredients in grams (search 'cookies recipe grams'). You'll need a kitchen scale, a bowl, a spoon or mixer, and a baking sheet lined with parchment, with the oven preheated to the recipe's temperature. Weigh your flour to within five grams of the recipe's amount instead of scooping with a cup. Beat the softened butter and sugar together, called creaming, until visibly lighter in colour, about two minutes. Mix in egg and vanilla. Fold in the weighed flour just until no dry streaks remain, then stop.
Bake at the recipe's stated temperature until the edges look set but the centers still look slightly underdone, and don't taste the raw dough. They firm up as they cool on the tray.
Don't keep mixing once the flour goes in just because the dough looks shaggy. Every extra minute of stirring develops more gluten, which is what turns cookies tough instead of tender.
The thing most people miss
I believed baking failures were mostly about the oven running hot or cold. What actually changed my understanding was learning that scooping flour with a cup can vary by a quarter or more between two people doing it exactly the same way, which explained my inconsistent results far better than the oven ever did.
Once I started weighing everything dry instead of trusting a cup, the same recipe finally came out the same way twice in a row, and the oven stopped being the thing I blamed.
What not to buy
Don't buy a stand mixer before a scale. A stand mixer saves effort creaming butter and sugar, but it can't fix inconsistent flour measurements, and that's the actual source of most inconsistent results for a beginner.
You'll know the scale earned its place the third time you bake the same recipe and it comes out identical to the first batch, not just close. Weigh the finished dough itself once, out of curiosity, and it'll likely land within a few grams across batches too. From there, pay attention to how long you actually cream the butter and sugar, since that single step changes texture more than any other step in the whole process.