The only fish I don't quarantine are ones I get from Severum Mama and HN1. However, if it is the first time stocking the tank...you can basically consider the main tank AS your QT. The main concern when adding new fish is that if you put them directly into a stocked tank...there is the risk of them infecting the fish you already have with a disease / parasite they bring in.
Keep in mind though, QT's are pretty much a must have item for a seasoned fish keeper. Even if your tank is fully stocked and you don't plan on adding more fish...the need occasionally arises when you need to set up a hospital tank to treat a sick or injured fish outside of the main tank.
Some people use Tupperware bins, but you can go to PetSmart and guy a 10 gallon tank for like $12.99. You don't need lights, substrate or decorations...just the tank, a heater and a cheap filter. It's always a good idea to run an additional HOB filter on your main tank, because if you ever need to set up a QT or hospital tank...you can do it in 5 minutes by simply filling the tank with water and pulling the extra filter off the main tank. That way you have an instantly cycled emergency tank