As far as gear, it really depends on what you're playing. Some guys like to stick with the Russian/eastern european theme, and buy guns and gear that fit the style. Others prefer the Brit/Aussie style, and still others the good 'ol classic US Special Ops with M4s and such.
If you're buying uniforms, be sure to get both a desert color and a forest color. Most groups do a
green vs. tan theme for their skirmishes. You'll probably be on green team some of the time and on tan team some of the time.
For load-bearing gear (or MOLLE, whatever you prefer).... just look at a honeysuckle-ton of pics of real soldiers. Find what looks good and what setup might work for you. I've gotten most of my stuff from these sites:
www.cheaperthandirt.com
www.evike.com
www.airsoftgi.com
They're all good and have a ton of gear and guns.
For gear... just start simple. Maybe buy a MOLLE plate carrier vest and a couple of STANAG pouches, a radio pouch (if you're using comms equipment, that is).... maybe a utility pouch. Dump pouch. And then set up your pouches however you think might be best for you. I like MOLLE because you can customize the layout for your personal needs. Take time to play games with new setups of your pouches; see if different configurations work better in the field for you.
As far as guns... Personally, I prefer the standard M4/M16. Nothing fancy. Maybe a cheap red-dot sight. I always use mid-size mags (70rds or so) because it's a bit more "realistic" and a lot of groups prefer them anyway. I haven't really gotten into customizing my guns very much... how they come out of the box always works great for me. For sniping, I'd probably run an M14 or EBR-style gun.
Hope some of that helped!
