Can I order new clothes for a date during the 9 days?
If you indeed need the new clothing for the date it is permitted. Although we don’t but new clothing during the nine days, dating for marriage is considered l’torech mitzvah, and therefore permitted. If the date is after the nine days and it can be ordered after Tisha B’av then it should not be ordered now.
O:CH 551-1, Shevet Halevi 9-131(4), Poskim.