My suggestion will be bitcoin or ethereum. But to daily trade, you can select bitcoin because the price is volatile, so you can hope that you can have a chance to buy low and sell high. It will not be easy if you don't have the skills to determine the time to buy and sell bitcoin at any price because you need to analyze the time to trade. And for ethereum, I think you can make short term trade which you can buy now at a low price, hold it for a while, and sell it when the price increase. But still, ethereum will follow with bitcoin price moves, so I think you can trade bitcoin pair USDT only so your chance to make a profit will bigger than to trade altcoin pair bitcoin or pair USDT.