Anyone know who is the most successful Seller in cgtraders? and by successful means how much they aproximately make monthly

Quality over quantity, not the other way round. As you already noticed by yourself, seller that has few, but very high quality assets, will always do better than seller with ton of shitmodels. Here's the list of sellers in cgtrader, more or less sorted by their success rate: https://www.cgtrader.com/designers Observing it closely, you can see what it takes to be successive at selling models. The very top dogs here has thousands of models, but that's mainly because they're not individuals, but group of designers. Nonetheless you can be very successive even if you're working alone, but you have to make high quality and unique assets that are in high demand. On the other hand, there are couple sellers whos models count is in a range of 100K, but the quality is so shity, that they just littering the search. They are so low in rank, that you have to go very deep into designers list to find them :]

The big names upload around 50 models every day, I'd imagine they make quite a lot of money. I remember one person on Youtube making a video about his cgtrader account and he had ~150 models and was making ~ 500$ a month, the models were really well made, high poly solid props, good topology and textures but nothing that had rigs/animations.

The key thing to always remember is the service being provided here is to save people time. I can never understand why poor models are uploaded even for a very low price. Anyone can make a low quality model & try to sell it on here, but they will then gain a reputation for low quality assets.
Also every now & then someone will ask me for help with a model they have bought. I am always happy to do this because I believe my assets are of good quality & every time I have been able to provide helpful support to customers.
I doubt I would be able to do this if I provided hundreds of models, as responding to support requests for lots of cheap models for say less than $10 would take too much of my time & potentially wasting the customers time waiting for me to respond - thus defeating the object of buying assets on here.

You can't buy a good reputation, but you can easily get a bad one for free with poor assets/support.

Ok so I switched to Blender from 3ds max as my native software about 2 years ago. I have used photoshop for 20 years now so I know my way around that for textures. One of the key skills I have is to fully unwrap my models to leave no overlapping UV's. This is so I can provide customers with an easy way to add their own textures using the unwrapped UV atlas as a guide.
Your jewelry models are very impressive- I would price a few of them higher though. Buyers may be applying a search filter which if they are looking for models over $10 but less than $50 yours will be left out of that search. Try pricing a few of them higher and see if you get more views or even sales. I would amend the stalk on your apple model to be a lot rougher/darker. It will help the apple itself look more punchy. I would increase the number of polys to about 2k per apple, this will give you the option to have more variation in each one & if there are say 5 in a scene it's still only 10k which would still be considered low poly. One last thing I would include a wireframe render for each angle you produce and a few renders zoomed right in to show buyers the level of detail always helps. Stick with Blender the payoff is worth it - it's more accepted now as proffesional software. Hope this helps - good luck!

Ok so I do my wireframe renders using a freestyle pass in Cycles. You select all your edges in edit mode then select mark freestyle edge. You can then activate the freestyle checkbox in your render settings under the properties. You fine tune this in the view layer properties. There should be plenty of tutorials on if you type "blender freestyle" in Youtube. Another thing which would help would be to get your printable models actually printed & add those as preview images. If customers see the quality of the final result it only increases the chance of a sale.
Glad i've helped, I think this goes with the attitude you find in the Blender/open source community, the better we perform in this industry & show a willingness to help - it becomes a better place for everyone. This can only be possible with a positive or at least a constructive attitude.

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Both quality and quantity are important