I'll answer your speaker wire question first since that's the easiest. For most applications 12 or 14 ga wire will be fine. For really short runs you could probably get by with 16-18 gauge. If you go a little heavier than what you need, you'll never have to worry about it.
As for starter speakers, that's a fairly open ended question. It depends on your budget. You should consider a decent sub along with some decent entry level speakers. Some suggestions: a sub from Hsu, SVS or AV123 and Hsu HB-1s, SVS SBS-01s, Infinity Primus 162s or Ascend CBM-170s. My suggestions are biased towards internet direct brands because I believe you can generally get more bang for the buck that way.
I tend to be suspicious of home theater in a box type systems. They are an improvement on the speakers in your TV but not too many sound really good compared to "real" speakers. If you want your system to sound good with music as well as movies, I'd stay away.
I don't know about the wireless speakers you mentioned. They may be fine for surrounds but I would prefer more traditional wired speakers. You trade running speaker wires for running power to the speakers. Plus, I have my doubts about what the sound quality might be like.
Jim