If you are taking the proper courses, getting good grades (B’s and above) and your test scores on the SAT or ACT are average you shouldn’t have any issue meeting the NCAA core requirements for DI or DII.
The absolute lowest GPA you can have and still be eligible is a 2.0 (it changes to 2.3 for the class of 2016 and later). A 2.0 (2.3 for class of 2016 and later) GPA will meet the requirement for DII. NCAA DI requirements use a combination of your GPA and your SAT. For example if you score 660 on the SAT (Math and Reading only), then you need to have a core course GPA of 2.9. The lower your GPA the higher your test scores need to be.
The only way to determine what your core course GPA is to use the NCAA worksheet. In order to complete the worksheet you need to get a copy of your transcripts and identify what classes meet the core course requirement. You then plug those courses into the worksheet and follow the instructions.
Once you have your core course GPA you can then go to the NCAA sliding scale and see what SAT or ACT score you need to achieve. Keep in mind, these are only minimum requirements. The GPA and test scores you would need to gain admission into a specific university will likely be different. This is why it is important to establish your academic goals with the college coaches recruiting you and not just based on the NCAA minimums.
Here is another NCAA guide for calculating your GPA