How times have changed.Buy a complete AR upper.
Buy a complete AR lower.
Put them together and boom Shaka laka. Go shoot and gave some fun. Don’t take on an M1a for your first. Too many special tools you won’t use again unless you intend on building more if the first goes well. Then there is the inexperience factor that could lead to undesired consequences.
An M14 was the first rifle I ever "built" because it offered the lowest investment in tools and parts . . .