You can start with a CAI and freer flowing exhaust, those are a couple good mods that work well with a programmer when it's available. The R/T's are sweet as is lol but there's lots of ideas in the HEMI mods section!
Hey there man. That's a good question. Not sure about the 2013's but they just released programmers for the earlier 4th gens. Problem was Chrysler locked down the computer with an encryption that was tough to crack and since the '13's are still relatively new, I honestly don't know if the programmers recently released would work or if you may have to wait for them to crack a new code but my feeling is you might be in for a wait, hopefully it won't be too long.