It is asking for my AGI from last year but this is my first year filing myself. Last year my dad claimed me. How do I answer for my AGI?

If you did not file a 2019 tax return then you can say you did not file a 2019 tax return, or you can use zero as your 2019 AGI.

If your 2019 AGI is causing your tax return to be rejected, you can try entering "0" instead. The IRS requires your 2019 AGI to verify your identity for e-filing. If you're paper-filing your return, you won't need your AGI because those are manually processed.