in which packages I can find data sets for RNA-Seq in edgeR, DESeq and others packages?
Could you recommend some data sets for beginners?
Have you red the DESeq2 manual? It is full of examples at the end. Each of them can be downloaded through R.
Same goes for edgeR, normally they include an example that you can reproduce yourself in the manuals
While DESeq2 includes a built-in data set for RNAseq (follow the guide here), you can find any number of real datasets in EBI-ENA or SRA.