Nice!! you got a sweet deal on your camera with really low usage then!! That's how it starts. You will know when you've outgrown it and time to move on, I started with second hand Nikon D40x and I used to get killer shots with, I miss it sometimes. Your camera as it stands even has some features that are better than mine (because my camera is like 8 or 9 yrs old, I only have like 14 mgpixel) Don't feel in a rush to upgrade your body and do research. A lot of people think photography is in the device and it does somewhat help but a lot of it is skill, light manipulation and framing. In other words, practice, trial and error and experience...lol. To get new lenses cheaper, sigma has good gear too but make sure you get one with the right canon mount ,they make lenses for many camera brands but don't cheap out too much, sometimes it's not worth it, read reviews first.

What lens do you have now and what are you looking to get?

Nikon like canon has the same lens mount for all the bodies across the Nikon brand except for the new mirrorless tech. Realistically you can buy mount adapters to use incompatible lens too. When I do go mirrorless, I will get one to be able to use my old lenses.