My question is if I could just up the HDD to like 1.5TB or if I should fork over the cash for an SSD?
The PC's main use will be for gaming and graphic design work. Also, any advice on anything is welcomed, this is my first ever PC I will be building.
SSDs are about speed, not capacity and it's totally up to your personal preferences what configuration you end up with. If you aren't too concerned with loading times, that's really the primary benefit of having an SSD. Still, it never hurts to install the operating system and your most common programs / games to an SSD, and then have a large HD for storage.