After getting DEGs number what next? means what I have to do further after getting annotation, pathways etc? what further we can do?
That depends on your "biological" question and your data. What question do you want to answer?
Its all depend on your work objectives because you can do "n" number of analysis in research.
Usually you validate the results (or at least a few interesting genes) in additional samples and then you're finished with that portion of a project.
Networks may be? Study their interactions/associations , identify hub genes etc.