shoes
Having reasonable footwear for tango can make all
the difference, particularly something that's
comfortable to move in and let's you pivot easily
on the ball of your foot. Sticky shoes (or bare feet
on the wrong floor) can make this hard to do,
and give your knees problems.
Although it's common for followers to wear heels,
and you certainly may, they are not necessary.
For practices like ours I recommend dance sneakers
or character shoes, as described below.
online

The Sansha Dynamo or Salsette are good tango shoes;
Amazon sells the salsette with a suede sole for $30 including shipping.
nydancestore.com also carries these :
The size of the Sansha shoes don't match street shoe sizes.
Usually the site gives a fitting guide.
For Sansha, women order about 1-2 sizes larger
than street shoes, men order 3-4 sizes larger.
(Mine is a size 14; my regular shoes size is 10.)
If instead you'd like something with a heel,

Amber has found this
New York T-Strap
2" heel character shoe very comfortable,
for about $35 at discountdance.com