I am a PC gamer who concentrates mostly on FPS and the odd RPG. However, my keyboard recently broke (use a horrible temporary replacement). So I need a new keyboard/mouse however I am not sure what to get.
But I am not sure on whether I need a gaming keyboard, I hear the main difference is the macros and backlight but I have some questions about the macros:
How useful are the macros? Could I say to:
1. automatically switch to a shotgun in HL2
2. access a particular item in Gmod
3. Use them in photoshop? if possible, for example I like to access an item with no shortcut can I set up a macro.
Macros are typically used on the keyboard. You can assign macros to any mouse, though it's obviously easier on a gaming mouse thanks to the extra keys and (presumably) easy to use software. So yes, you could do all of the things you asked with using a gaming, or otherwise, mouse.
G15 and G11 are older models, and I would suggest the G17 for a cheaper, newer model or the G19 if you don't have a problem with money. Considering that you're looking at the MX518 instead of the G9x/G500, I'll assume you do.
There are several models for the G11 and G15, so I'd suggest you look into which fits your needs best. I'd recommend other keyboards and mice, but once again, I don't know what your needs are, so spouting names might not be so helpful.