The best kettlebell size for you is one that feels manageable enough to lift but heavy enough that your muscles feel exhausted during the last few reps of each set.
If you're looking to buy kettlebells, it might be a good idea to go to the gym to test which size feels right for you. Our kettlebells come in standard sizes and you will get a good idea of the weight at the gym. Try doing 3 sets of 10 reps for a few different exercises and note down which weight exhausts your muscles. If you can't get to the gym we recommend the JTX 6KG Kettlebell if you haven't done any weight training before.
If you're looking to buy kettlebells to strengthen and build your muscles, we recommend investing in a set. With only one kettlebell you'll be able to strengthen and build your muscles to an extent that will be enough for most people. You can do this by increasing the number of reps, or sets, you perform over time. However, there will come a time where your kettlebell doesn't exhaust your muscles anymore. At this point, your exercises will be toning, but not building muscle. With multiple kettlebells you'll be able to move up a weight when you're ready or swap to lower weights for weight training weaker areas of your body.