Generally speaking, the weight of hard darts is between 20 and 25 grams. Soft darts are generally18g, and the lightest is16g. In addition, it depends on what kind of darts you use, such as straight tube, torpedo or other shapes. There are many reference factors in choosing darts, and you won't know until you try it yourself.
In addition, when you practice for a period of time, with the improvement of the qualitative and level of movements, your own understanding of darts will also improve, and you will make up your mind to choose darts!
Personally, don't use too light darts. Beginners have limited control and feel of darts, and light darts are not conducive to practicing movements. Hard darts are recommended to be more than 22 grams.