Try different ones and see which interface works best for you.
I tried
Comus Thumbs at first and couldn't stand it (but that's just me - other people love it) so I gave
VanillaTGP a shot and felt comfortable with it. Both are free if you allow them to skim some of your traffic. When your site grows you can still buy a licence and keep all traffic for yourself.
As for trading scripts - I like
Arrowtrader for its nice and clean interface, but there are a dozen or so alternatives out there too.