What for you is the best gaming RAM? My personal preferences are Corsair Dominator Platinum Series, Kingston HyperX FURY and Patriot Viper 3 Series, Black Mamba. Provide yours and the pros and cons if you may.
Depends somewhat on what CPU the RAM is being paired with, but generally speaking the differences between various speeds and timings of memory is fairly minimal - when it comes to game performance, at least. I tend to recommend something like a Corsair Vengeance LPX kit: just $75 for 16 GiB, plenty of performance and solid stability.
I think it depends on the rest of your build. If you have a B360 motherboard, it may not be worth upgrading to Z370 just to get faster memory. Price wise, 2400 to 3000 isn't too bad it's only like $10 more if you compare 16 GB. However including motherboard upgrade makes you add another $50 or so which just isn't worth it.