To claim EITC, Should I use my AGI or GI ? which one is correct to check my EITC credit? I think AGI, but someone told me should be Gross income, I am confused?

It's AGI and Earned Income both have to be less than the table.  Do you have children?  You can qualify for the EIC without a qualifying child if you are at least age 25 but under age 65 and your earned income and AGI are both less than the lowest amounts on the table which for 2019 is $15,570 ($21,370  married filing jointly).

You can not get the EIC if you file Married Filing Separately.

You can not get the EIC if you are a dependent on someone else's return.

Income from a K-1 does not count as earned income for the EIC.

The EIC is a refundable credit, meaning you can get it even if you owe no income tax.

Here are 2  Turbo Tax articles on the EIC Earned Income Credit……

http://turbotax.intuit.com/tax-tools/tax-tips/Tax-Deductions-and-Credits/Earned-Income-Credit/INF12034.html?_requestid=307561

https://ttlc.intuit.com/community/credits-and-deductions/help/what-are-the-qualifications-for-the-earned-income-credit-eic-or-eitc/00/25603