Given your age, I'm assuming you mean to purchase a rifle.
Your primary ID is always your state issued picture ID.
The secondary ID (unless they've changed it lately) can include a utility bill that shows the same address as your picture ID, I THINK you can use a bank statement as well, and I know that a Voter's Registration Card is also gold.
From Virginia law on firearms purchase requirements:
"To establish personal identification and residence in Virginia for purposes of this section, a dealer must require any prospective purchaser to present one photo-identification form issued by a governmental agency of the Commonwealth or by the United States Department of Defense, and other documentation of residence. Except where the photo-identification was issued by the United States Department of Defense, the other documentation of residence shall show an address identical to that shown on the photo-identification form, such as evidence of currently paid personal property tax or real estate tax, or a current (a) lease, (b) utility or telephone bill, (c) voter registration card, (d) bank check, (e) passport, (f) automobile registration, or (g) hunting or fishing license; other current identification allowed as evidence of residency by Part 178.124 of Title 27 of the Code of Federal Regulations and ATF Ruling 2001-5; or other documentation of residence determined to be acceptable by the Department of Criminal Justice Services, that corroborates that the prospective purchaser currently resides in Virginia."
I believe that, if you're buying an "assault rifle," you need to also prove citizenship...
OK, from the Virginia law on assault weapons (yes, I know, they're not assault weapons)
"In addition, no dealer shall sell, rent, trade or transfer from his inventory any assault firearm to any person who is not a citizen of the United States or who is not a person lawfully admitted for permanent residence. To establish citizenship or lawful admission for a permanent residence for purposes of purchasing an assault firearm, a dealer shall require a prospective purchaser to present a certified birth certificate or a certificate of birth abroad issued by the United States State Department, a certificate of citizenship or a certificate of naturalization issued by the United States Citizenship and Immigration Services, an unexpired U.S. passport, a United States citizen identification card, a current voter registration card, a current selective service registration card, or an immigrant visa or other documentation of status as a person lawfully admitted for permanent residence issued by the United States Citizenship and Immigration Services."
