Do you plan to CCW, then a baby Glock like the G26 or G27 would be a great choice. If not, then maybe go for the compact sizes like the G19 or G23.
Be sure to handle both the Gen 3 and Gen 4, a lot of people like the feel of the smaller Gen 4 (and it does come with extra backstraps to enlarge the grip to Gen 3 size and even larger). I love my 23Gen4. And not unhappy with the older ones either.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek