One of my grandfather's hobbies is photography and he wanted a computer to store the photos and edit them. I tried to future-proof with a six core processor and ample storage. I also got a nice, large QHD screen to view the pictures on.
This was my first time building in a small form factor case. The big thing I had to worry about was making space so that the one intake fan could supply air to the cpu cooler (stock intel). I bought two 80mm fans because it said there was space for them, but then the manual said they wouldn't fit with a double slot graphics card, which I got. One thing I would recommend is to buy a fully modular power supply when working in a small case. I had a lot of extra cables that I had to tie away and they are just decreasing airflow.
I also did this to prove to him that I could build a computer for cheaper than getting a pre-built. Basically what I found was ~$150 or about 15% savings in parts.