I'm surprised no one mentioned it yet, but invest in a good pair of boots. It's definitely something you don't want to overlook, especially when playing in forested areas or area's with tricky terrain.
You don't want to bust an ankle and get put out of the game for a week or two.
Knee pads are another thing you might want to look into.
If you wear glasses, definitely get something well ventilated with a fan or maybe consider picking up some daily contact lenses (Been working great for me), would save you from having fogging issues with glasses. Goggles fogging up is already an issue, don't want to deal with glasses as well if you can avoid it.
Just your friendly neighborhood narcissist gearwhore.