You can ride in whatever you want to be comfortable. But be careful, first it's shorts, then you go bibs. Somewhere along the line you pick up gloves and a helmet for safety. Then it's a jersey, followed by cycling shoes. Finally you are fully kitted out and looking at what you can do to upgrade your bike, unless of course you just buy a new bike. And then the new bike will need titanium bling and other weight weiney esoterica.
There is a reason there are so many addiction threads. This one has 247 pages.