Understanding optics and reticles
There is so much back and forth behavior when it comes to accessorizing AR15 guns and and the optics that go on them. Luckily I was not in the category of people that spent $1000 on optics and then switched to something else later. I was smart enough and had enough life experience and also a very small amount of money in a bank account so I started off with an AR15A2. I still believe that after starting a new shooter out on a 22lr rifle preferable a bolt action, once a shooter can handle a 22lr gun, the AR15A2 is the next best step.
When it comes to not having a lot of money to spend but you know you want serious equipment, it really comes down to Trijicon, Aimpoint and Eotech. There are pros and cons of each but none of them will do everything. Trijicon Rifle Scopes and give you a very wide range of optics for hunting and combat but to this day the Eotech still holds its own for close up fighting and fast shooting. In close range fighting zero magnification is the best but there are some options like the TA26 which is 1.5x magnification and gives you a light edge over zero mag. This may mean the difference between identifying a weapon from a cell phone at reasonable close ranges.