Tango is a chance to be sexy and show off. People should wear whatever they want. One of the great things about tango is that “No one will ever say ‘You’re too old to be wearing that’.” It’s clearly untenable to get prudish about the dance which is already perceived to be pure sex.
Wear whatever makes you feel sexy. I see no reason whatsoever to wear technical dance shoes, and several reasons not to. Like clothing, there are a few functional requirements, but many non-dance shoes meet these requirements, while looking and feeling much better than tango shoes.
You will need to feel great. Bring whatever makes you feel Sexy Sexy Sexy (daytime stuff too). Do not pack anything that you feel so-so in. You won’t even want to go to the grocery store in it.
The main thing to pay attention to when shopping and dressing is how a piece of clothing makes you feel. Notice if you are smiling, notice if you are twirling or tapping your feet. If this piece of clothing gives you joy and makes you want to dance, then it’s a keeper. If you’re feeling doubtful or self-conscious, take it off!