I am currently mining in solo.ckpool with my recently acquired S3 (I paid 20 dollars second hand for it) and I have been mining for 10 hours and nothing. I know that it is a very low-power equipment, that's why I wanted to ask you if you recommend me to continue mining in that pool or change to another and Kas mines for example. I don't know, I'm really lost. If you can guide me I would be very grateful. All the best.
As BitMaxz said, you are currently mining on a solo pool, so unless you find a block, you will have nothing. Your reward is 6.25 BTC (+ tx fees) or nothing. And if you take 0.5 Th/s on SoloChance.com, it gives you the following estimation :
Between 12000 and 13000 years with an average luck, so your chances of getting a reward are small. You can keep mining on solo.ckpool.org if you want like a lottery ticket. You can be very luck and have a block. Or you could earn nothing at all.
If you want to earn some sats, you can always try to mine on
ViaBTC, at least they pay the transaction fees to the miners.
I hope that you pay very low amount per kw/h, because the S3 is not the top ASIC regarding efficiency.