Jose, as shown by the wire table in the Russell table which Randy linked, for even the longest 30' run to surrounds, 16ga wire should be plenty for the type speakers you'd use there. 100' of the CL2 rated wire from MonoPrice, as Randy also linked, would be a good buy.
Incidentally, if you haven't done so, besides the wire table, it'd be worthwhile to study the entire Russell speaker wire explanation. This has educated numerous listeners about the facts on this topic and helped them avoid the charlatans selling magic wires who pollute the audio industry.
As to coaxial cables with RCA plugs for your subs, I'd suggest the same cable I use with my EP500 from MonoPrice here
. These are not too thick and are relatively flexible and do this simple job as well as it can be done.