I personally use a SteelSeries Sensei Raw and i love it. It is an Ambidextrous mouse so it can be used with either hand. To the people discussing Razer products....I personally do no like Razer things since they have a tendency of breaking. My friend has a DeathAdder, and he was one of the few lucky ones whose mouse didn't break. As for a keyboard, I just ordered this for $80:
http://www.amazon.com/gp/product/B00DKXXAIS/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1
But the important thing is with mechanical keyboards is the type of swtiches inside them. Some keyboard's use different ones, like the Razer BlackWidow uses blue switches.
I will make a quick little table to describe these switches:
There are Four main switches: Blue, Red, Brown, and Black.
Before i start i must say, the force actuation isnt always accurate, i'm just using the force needed from a site:
http://elitekeyboards.com/support.php?lang=en#1a
Cherry MX Blue:
Actuation Force needed: 45 - 60cN
Tactile bump?: Yes
noise: Audible click
Cherry MX Brown: 45 - 60cN
Actuation Force needed:
Tactile bump?: Yes
noise: subtle
Cherry MX Red:
Actuation Force needed: 30 - 60cN
Tactile bump?: No, linear
noise: Subtle
Cherry MX Black:
Actuation Force needed: 60 - 80cN
Tactile bump?: No, linear
noise: Subtle
So LSS (Long Story Short) When it comes to Mouses, it's about the "Feel" as well as the Durability, and little features it comes with, Like i mentioned before, I have the SteelSeries Sensei Raw and i love it. Had it for a year now and no problems, and it has two programmable buttons on each side which i use for each type of grenade on Counter-Strike. As for a Keyboard, it comes down to what type of switches you want and how you use a keybaord. You a heavy typer? Try the Black's, Like me and you want a "linear" keyboard that activates the keys easily? Try the Red's. Or you want to hear your keys and dont want to press the key's down far to activate them? Try either Blues or Brown's, Brown's for silence, Blue's for click.
As for what you should choose? Well...Which one do you want more? are you okay with your keyboard at the moment? then do a mouse. Personally i got a gaming mouse first because i felt like it was more important. So you decide, Please let me know what you decide to go with, im curious.