Any kettlebell is better than no kettlbell.
But if you're going to purchase a kettlebell... I recommend a cast iron kettlebell.
My favorite company is still Rogue. I love their bells.
This kettlebell 40lb is made by Rep Fitness and I love this the handle, it's a little thinner and perfect for a woman's grip.
But the gab between the handle and the bell is too big so I like to wear wrist guards. Tradeoffs.
If it's in your budget, I recommend Rogue kettlebells. Once you buy one... you'll end up passing it down in your will. It will last forever.
If it's not in your budget...
I recommend any kettlebell where the bell is round.
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Don't bother with any of the funky shapes...
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Dont' bother with the dumbbell kettlebell contraptions...
Get a round bell even if it's rubber coated.
When it comes to weight...
I recommend starting with an 18lb and a 26lb bell but when you go to order them, they'll be in kilograms... so it's 8kg and 12kg you're looking for.
Let me know if you have specific questions... I'll help you make the right decision.