depending on what your looking to spend, it can really range. I personally have ecm link v3 from ecmtuning.com for the full version it cost around 500 plus shipping. decent amount but worth it in my opinion. I know there is cheaper ones out there, like AFSC but you can really only adjust fueling then.

IMO ecmlink is way to go. Youll have to pay for it but best IMO. Also with ecmlink there are a lot of people out there to help you with tunning. They even have a guy on here that will remotely tune it for you.

you can log fuel trims, knock, and check codes, its ok to start with, had to get rid of it and get get link.

If you do go with link though, you wanna check to see if your ecu is socketed already if it isn't it will cost a bit more then 500. also another perk with link theres plenty of helpful videos and an entire wiki of written out explanations of things for getting started. just give yourself a good solid weekend to mess with it because when you put the chip in your pretty much installing a blank ecu that you have to program before you can really drive the car.

epromid [ECMTuning - wiki]

socketid [ECMTuning - wiki]

dsmlinkloggableparams [ECMTuning - wiki]