I want to buy/build a new desktop that can handle basic computer games (League of Legends) and MMO games to come for the next 2-3 yrs.

I wish to play these games on high quality and basically will only be using the pc for gaming and my laptop for work. I have never build a desktop but I am willing to give it a shot if it isn't incredibly hard. I am looking to spend between $500-1000 but as long as it can handle the games on high quality it will be fine. Can anyone give me suggestions on computers to buy online ( ie. digitalstorm, alienware, etc) or sites where I can customize a desktop. Additionally, if you could give me suggested parts for a computer I would build that'd be great too! If this is in the wrong subreddit please redirect me. Thanks everyone!