Reddit mentions of Smart & Sexy Shaping Skirt (XL, Black)

Up top: standard issue plunge/push-up bra with a tank or whatever over it. Depending on the bra and rave in question, the word "nothing" should be included in the concept of "whatever" :D ). I say standard-issue, but if you've got one of the hard-to-find sizes that are all so typical 'round these parts, you might well look for something by Lula Lu https://www.lulalu.com/t/category/bras/

For the bottom, your answer is to be found in the shapewear section of your favorite physical or online womenswear store:

• if you want to hold a tuck, something like http://www.amazon.com/Jockey-Womens-Skimmies-Slipshort-SMALL/dp/B011YKMITA/ is in order.
  
  
• if you want to avoid a tight tuck yet minimize/eliminate distinctive bulges (and plan on wearing a dress or skirt), then look at this kind of thing: http://www.amazon.com/Smart-Sexy-Shaping-Skirt-Black/dp/B019774XBI/. Sometimes these things have seams that make them suitable only for underwear, but many just look like a bodycon skirt and can be worn straight up (particularly in situations like raves)
  
  It's going to be up to you to figure out where the compromise between the desired level of control and the desired level of comfort is. :D