One of my biggest questions, before I did my first race, was what am I supposed to wear while competing during three 3 different sports? You get in the water get out of the water ride your bike and then run for a bit. The number one thing I knew was that I had to be comfortable but is there a way to condense all three activities into one outfit. The answer is yes. There is an article of clothing that you can swim, bike, and run in. This is called a tri suit! On average, they go for about 100.00 dollars. This may be a bit of a hefty price luckily there's a compromise. I have never owned a tri suit but I do own plenty of bathing suits and workout clothes. So I usually swim in a one piece suit. In the transition area, you can leave your sneakers and spandex short and a t-shirt, specifics can vary based on weather. Then you're pretty much set for the rest of the race.
I have a few accessories for racing. Wetsuits are sometimes needed due to the cold temperatures. Those who are new to the water also tend to wear them to provide comfort and confidence. If you are racing in the earlier or last months of the season the likelihood that your gonna need a wetsuit is pretty high so if your racing around then I would make sure you have one.
Another accessory is biking cleats. Definitely not necessary but they are helpful on the bike as they help make you're pedaling more efficient! if you don't have them that's ok you can just ride with sneakers.
The last accessory I would recommend is a hat made for working out. A hat that is made for wiping away sweat and blocking out the sun! I have a brooks hat its super light and keeps you nice and dry!