Why you have USDT anyway? That wont give you any profits but only security from getting your investment going up and down as its price is always stable.
Well you should choose wide range of altcoins now as this is completely perfect opportunity for you to get in. I think you should go for Top 10 coins as they will bring you at most surety that you will have profits back to you at some point in the future. Always remember that after each down trend there comes the perfect up surges in the crypto. So current time is heavenly, try to get many coins rather than the selected ones. Also get your hands on undervalued coins also, currently they are popular as well.