I would buy A4 (or US letter size, depending where you are) sample packs from Canson and Hahnemühle at the very least. You can get bogged down with too much sample paper, but I would also look at Harman, Innova has free sample packs on their US website, Museo, and Moab.
As for textured papers, it depends on how heavily textured you want. I like Hahnemühle German Etching for a medium textured paper that holds detail very well. Really, there are too many to go through, everything from very lightly textured vellums and Japanese rice papers, to heavily textured watercolor papers.
If you are in the US, then itSupplies/Atlex has a samples page:http://www.itsupplies.com/Samples
as does B&H: http://www.bhphotovideo.com/c/search?atclk=Type%2fStyle_Sampler&ci=1118&N=4077634583+4294954869