Samba Whites!
"Samba Whites" is a short-hand term for describing the "all white" attire that we
often use for the bateria costume.  Even when we have an elaborate head piece
of shoulder piece, the required dress for under the costume is often all white.
White Shirt
Any all white shirt or t-shirt will do.  The more dedicated bateria member would have an all white, collared, short or long sleeved dress-shirt clean and ready at all times!  Many of us use the quite chic and smart looking Guayabera Shirts which were used for our costume in 2000.  (Note: The link is a quick way to view and purchase on-line, but the shirts are widely available in the local Mexican Western Wear shops in the SF Bay Area.  I buy mine at the San Jose Flea Market for under 20 bucks.)

White Pants
Any all white pants will do.  The more dedicated bateria member would not use anything that looked too much like sweat pants.  However bright white sweat pants are better than off-white or beige pants of a more formal nature.  Kmart and Target usually have painter's pants, which are usually made from white heavy duty denim.  I recently found some good comfortable white pants at SmartScrubs (there is a real store in the Great Mall of Milpitis).  Although some of the "scrubs" look a bit like sweat pants, I think "Genes" line looks pretty sharp, and features a Surdo Mallot loop!

White Shoes
Any all white shoes will do.  The more dedicated bateria member would have a shiny set of white patent leather shoes, however, I believe that approach is excessive.  I have always used cheap white loafers.  Sometimes I use a white paint to cover a small blue stripe often found on cheap white loafers.  Kmart has these shoes at this time for under ten bucks.  There is a product called "Shoe White" which restores dirty shoes to a bright white luster.