i think the best pair are BTC USDT ? is possible to trade only this or need difference the crypto ?
Day trading is the best way to earn from this dip other than holding. Day trading, I believe, is simply taking advantage of the volatility of cryptocurrencies within the hours of the day.
Day trading, however, can be very risky if one is not very careful. I believe you can earn even more than $50 if you have a huge capital and you understand how the market works.
You will, however, need to diversify into different coins if you want that much profit. It's not enough to focus only USD:BTC trading. There are times when the price of bitcoin will go downward and you won't make profit from it but with diversification, you will be able to make profits from other coins as well.