MP15 Sport is definitely a good starter AR. Only real downside is the lack of a chrome lined barrel. Since guns are almost always a one time purchase, I spent a bit more and got a Daniel Defense M4V4.
Good luck getting anything during this craze.
130is Alpineweiss 6MT M-Sport / SuperSprint Headers with Swain Tech Race Coat / DISA Manifold / EVOLVE Tune / TCK DA Coilovers / Euro CF Intake/Box / BMW v1 Wheel / BBS RGRs with PSS / F30 Brake Shield / BMW CF Spoiler & Diffuser / Blackline Tails / Rear Fogs Enabled / Front Fogs Delete / CDV Delete / BMW Black Kidneys / M5 Illuminated Knob / BMW Stripe