Thread: Question on my first AR.

Sounds all good.
Yes, you can use a carbine or rifle buffer/stock on a mid length AR. Carbine buffer gives you more options for an adjustable stock obviously. The adjustable rifle stocks are pricey.
But main things with an AR are a good barrel, trigger and bolt carrier group.
All the rest can be any of the mid price range parts, you don't have to break the bank for those.