tMap is the most important component and if you are dealing with files then you should know tfile<input/output>delimited, tfile<input/output>excel,tfile<input/output>XML etc like wise if you are dealing with databases then you should be aware of db components.
Well with respect to Talend i would say you better start working on Tmap,not only because it is a important component or crucial component etc...it builds your logic and lets you understand the data flow. later you can move on to Processing family and then Orchestration and then Files and last but not the least the DB components.
On top of that, I would suggest to go through the syllabus of DI basics, DI advanced, Bigdata Basics and Bigdata advanced in the same order.
In this way, you will see different components during your journey and will learn about them. Again, the components you will be using really depends on your project needs and use cases.
