A leotard, also known as a one piece bathing suit (or swimsuit) is a garment invented by a French acrobat (Jules Leotard), which represents the best solution when it comes to ladies' wrestling attires, for several reasons.
The leotard is a simple clothing item. It covers the entire upper body of the lady wrestler, offering her perfect protection against wardrobe malfunctions. For those who will argue that the leotard covers up too much: it does, but it does it in an extremely peculiar fashion, which, instead of taking away from the visual impressiveness of the female wrestler's body, adds to it.
Leotards/bathing suits are or several different types, and they are made out of various materials too. There are matte cotton leotards out there, but as far as I'm concerned, these are unsuited for women's wrestling so I'm not going to go into detail on them. They do tend to cover up without accentuating the curves, they retain moisture from sweat and overall they're just unspectacular.

Women's wrestling is a highly visual form of sports entertainment, therefore lady wrestlers leotards should be flashy, form-fitting and preferably shiny-glittery. Quite possibly the best material to make ladies' wrestling leotards from is shiny nylon lycra. Shiny nylon lycra is made up of about 20% spandex (tightness and form-fitting-ness assured) and 80% nylon (which is responsible for the sheen, and thus for the overall curve accentuating effect). These percentages can differ. Some nylon lycra brands contain less spandex and more nylon. Such leotards are usually shinier but less stretchy. The perfect nylon-spandex ratio is in the 80-20/85-15% range. Shiny nylon-lycra leotards hug the body in the perfect way. They accentuate every curve while completely covering up imperfections. A shiny nylon-lycra leotard clad lady wrestler will look like a mean lean wrestling machine, sporty yet sexy, extremely well-displayed yet covered up and made safe from all types of accidents that can happen during the rough and tumble activity that wrestling is supposed to be.
Here's a list of various types of shiny nylon-lycra blend leotards that female wrestlers have used in the past and should stick with in the future.

   The plain-old, full bottom one piece bathing suit. On the right type of body all such bathing suits look great. Sporty and aggressive, yet really feminine in the same time.
Such leotards in black can be worn with just about any type of pantyhose (or sans) and any type of in-ring character. They can feature various patterns, they can be augmented with flowers and other accessories. Other solid colors, such as neon pink and neon green can be used as well, they'll look spectacular in the ring regardless of the type of gimmick the wrestling girl is trying to pull. For heeling, black is obviously the better choice. Neon Pink and Neon Green are more suited for clueless rookie babyfaces, while royal blue and red suit seasoned and skilled "faces" best.

Black base-color leotards with white or rainbow-colored dots on them are rather impressive too, whether worn by villains, faces or rookies.
Wearing a pantyhose is recommended under all leotard variants, because in spite of all the advantages they offer, leotards have a major shortcoming: with all the jumping, falling and twisting around involved in wrestling, they tend to ride up. Some of the lady wrestlers intentionally pull their opponents' leotards forcing them to ride up. Pantyhose offer great protection against this phenomenon, so arm yourself with a nice shiny pair and you can forget about picking your wedgie. Full bottom leotards come in a variety of cuts too. Some of them are higher cut, others are lower. I personally prefer those a little higher cut, but low cut ones are great too if you're going for the classic lady-wrestler image.

Pick one that you're comfortable with, because you do not need wardrobe-related distractions once you step into that squared circle. Just remember, higher cut leotards make your legs look longer while low-cut ones chop away at the apparent length of your legs.

   Thong leotards are a breed apart and I have to confess I'm a truly huge fan of these leotards. They're simply awesome, highlighting every asset of a nice body, while offering an unprecedented freedom of movement too. Thong leotards rock, but when it comes to wrestling, you absolutely MUST wear pantyhose under them. You see, when riding up, these guys can give an entirely different meaning to the term "butt-floss". Most people believe that all thong leotards are very high cut. They're not. Some of them are but some of them look just like regular full bottoms from the front, only revealing the thong part once the rear comes into the limelight.

Thong leotards, just like full bottom ones, can feature regular tank backs, racer backs, criss-cross ones or even turtle-necks. Make your pick according to your preference, but know that for practical purposes, there's no difference between these variants. Criss-cross back leotards may be a tad uncomfortable if too tight, and tank leotards may give you some problems if a strap slips off your shoulder (not likely in case of a tight enough one though). Racer back leotards are absolutely bomb-proof though and so are turtle neck ones.

   Competition leotards used for gymnastics are excellent for wrestling too. These feature long sleeves, which means they offer added protection. I'm personally crazy about such competition leotards. These too come in a wild range of colors and patterns. There are higher and lower cut competition leotards too and even thong ones (extremely rare, but I've seen some for sale somewhere). The cool thing about the gymnastics leotard is that it acts as a second skin: it covers your entire upper body, including the arms, giving it a nice sheen while not restricting motion in any way. I prefer to wear pantyhose with my competition leotards, but the lower cut ones can be used without such accessories.
As I said above, nylon lycra is an excellent material when it comes to leotards. It has a strangely appealing sheen to it, it allows for great freedom of movement and when it comes to sweat, it wicks moisture away from the body, trapping it and not letting it come into contact with skin again.

   Foil leotards are made of a sort of nylon lycra which presents an extremely high sheen. These leotards are basically metallic ones. Dressed in such a leo, you'll look like the female version of the T1000, which is great when it comes to wrestling and the whole showboating thing surrounding it. They make all sorts of leotards: full bottom tank, thong and competition ones using this spectacular material, in all sorts of colors and patterns. If you're looking to make an impression in the ring, by all means do go for one of these foil leotards.

Pictures of various leotards suited for women's wrestling: