For me, the most important pairs are Bitcoin and Ethereum. These are two fundamental currencies, without which I see no sense in the exchange.
They are the leading coins of crypto, therefore they could always be included in mostly all exchanges. USDT pairs is just newly added but it only few exchanges and only for the countries that USD is used.
Still be BTC and ETH will be a good pairs for me since we can easily convert it into our local currency directly.