I'm looking for a new wheelset for my 2009 Specialized Tarmac Elite. Currently, it is in the stock setup -- Mavic CXP 22 rims laced to Specialized hubs. I feel that my current set is a bit heavy on hills, but I have never upgraded my wheelset before and am not really too sure about what to look for. I think I want something lighter, but it has to be pretty strong because this is my only road bike and therefore goes everywhere and through everything -- if possible, I would like to get into cat 4 or 3 racing. Also, it needs to be clincher compatible and fit a 10-speed Shimano cassette.

I also would prefer something without a super weird spoke setup so I can true it on a stand without some complicated method. I'm only about 135-140 lbs, so it doesn't have to have a lot of spokes though.

What should I look for when choosing a new wheelset/any recommendations? And if I sold my current wheels in good condition, what could they probably go for?

I'll make one suggestion for your weight and style: Soul s2.0 (just come out with new hub design).
These are very stiff wheels.

First of all you need to set a budget. A decent upgrade will cost at minimum ~ $400.

You do realize that in this sport those two words are often found on the opposite end of the spectrum? What do you mean by "therefore goes everywhere and through everything"? Dirt/gravel/chipseal roads? Light off-road trails?

No one is going to buy a 6 year old stock wheelset unless you start the ebay bidding at 0.99 with no reserve. It probably won't sell for much more than that.

Also, you can buy a 11 speed wheel and just use a spacer so that it will be compatible with your 10 speed cassette. Some wheels will come with the spacer, otherwise you can buy it for ~$10.

Ultegra 6800 is usually a decent do it all wheelset. Fulcrum racing 3 is also very good for its price, but I'm not sure it will be your "goes everywhere and through everything" wheel.