The most coin I trade is bitcoin pair usdt, but I also trade altcoin pair bitcoin to increase my btc. So far, I usually trade ethereum, litecoin, xrp, and the other cheap coin price. But sometimes, I trade altcoin pair usdt too if I see the price can start increase and it would give me an extra usdt. And if the market shows good movements, I think my profit will increase too, and so far, I can get a nice profit from my trade although I don't trade for daily.
For me, I really do not have specific coin to trade, as most of the coins anyway depends on how I am able to analyze them being a long term trader. I am a swing trader, and I look out for long term trends and that is good enough for me. Sure, I just do not trade any coin I see, but I make sure it is a coin with potential and not just some shit coin and it is a coin with lot of trading volume so I do not get lost looking to sell my position as time goes on.