building your own is always better and you can get a more capable rig with less money. Building it will be way easier than you think. The hardest part for a beginner will be choosing the components. Just do your research and ask for help and revision in the "Systems" section of the forum.
actually the hardest part is if you try to fit an atx motherboard with only 2mm to spare with getting it in.
dont get me started on the cable management
(i know because of airflow but why do we try to get it as neat as possible with all cables hidden away when we usually don't even have windows on the side of the case so we cant see in?)
seriously though, if you buy all the parts someone on a similar budget chose. there are very good instructions in the motherboard manual nowadays with pictures to show which parts go where and they are very clearly labeled.
get someone to help if help is available then after first pc you will think. why didn't i try it sooner?