I wouldn't buy a case for 120...
Rather get something cheaper.
Sharkoon T9 Value Red ATX Midi Tower for like 70 € - solid case, good quality, nice features (I've got one without LEDs)
The money you're saving u could put in a better GPU. (saving ~ 50 with the case, + another 50 with 8 gig ram, + the 30 you have left to your limit). Plus, RAM is something your cousin could easily buy later. Graphics - not so much.
With the amount you save you could easily get a GTX 970 or similar card.
If your cousin is a gamer, he should spend money on gaming parts. not on cases IMO