I would try to get AV'd first if you havent already and then get access to all the classifieds on here. From there you can see that you have lots of high quality option for first guns.
If you plan on tinkering with your gun you may want to consider the M4 platform due to there being a plethora of after market support for it.
An AUG would be neat because they are not as common as most guns. Maybe you can consider a G36 platform as well.