Capital gains will be income for you on your taxes. How much it effects your taxes depends on several things. For instance, if you qualify for an Auto-Zero EFC based on your mother’s income then it won’t effect it at all. If you don’t, student income is hit the hardest of anything on the FAFSA at 50%. But, there is an allowance of $6840 that is protected, so you can make that much in a year without it counting against you.
Here is the actual formula if you want to work through it yourself.