I have developer, fixer, and stop bath concentrate. To make solution we usually use mixing jug/beaker.
Should we dedicate one mixing jug for each one of the component above? Or can we just use one for three of them?
You can use the same container and mixing utensils and thermometer etc. for mixing. This is valid provided you take care to rinse well between solutions. Also, the items must not be porous (ceramic etc.). If you are in doubt regarding your ability to properly rinse, you can still proceed if containers and utensils are seasoned. To season, save small quantities of the fluids for this purpose. Rinse thoroughly then season with a dilute solution. Suppose you are to prepare a developer solution and are in doubt as to the cleanliness. Rinse with a dilute solution of developer (may be used or otherwise expired), then rinse with clean water. This act will prevent contamination due to improper cleansing.
While you can use the same mixing jug, provided some precautions as Alan Marcus mentions...I'm somewhat confused as to the why of this. Ideally, you've got separate storage containers for your mixed stop, fix, and perma-wash (and photo Flo, if you use it). You can measure your chemicals in your measuring device of choice and then add to your storage container filled with the awaiting water1. Doing this, the only thing that you reuse is the measuring device.
In addition to what Marcus said about rinsing and seasoning methods - go in order of development. Mix up your stop batch, then fix, then perma-wash. Even if you were drastically sloppy, a little bit of leftover fix in the perma-wash won't kill a full batch, (though you may reduce the life of the batch). Going the other way around can really mess things up for you.
1: Adding strong acids/bases and water together releases a lot of heat. Because of this, it's a good idea to add acid/base to water (instead of water to acid/base) and to go slowly. Now, photo chemistry is fairly benign - but I'd encourage the practice anyway, along with good chemistry lab practices in general, in case you decide to get into more caustic photo chemistry later. You'll have a good base of second-nature skills.