For me i would suggest to buy usdt pairs, it us trending right now that usdt pairs is profitable when you choose the right alt coin pair on usdt, with low cost fee you can trade low amount of it and you may become effecient in trading
some ALT pairs with stable assets have indeed become more popular with low trading costs. many day traders use it because of the more stable storage of asset values.
but for investors of certain coins like BTC, of course, they will sell their altcoins on BTC pairs to collect more BTC.