League of Legends is one of the older games, and so it doesn’t require high-end hardware. Some things, like a decent CPU with a lightweight dedicated GPU, and some spare RAM is good enough for the average gamer.
If you are considering desktops, then here are some good options for you:
HP OMEN 30L Gaming PC
Thermaltake LCGS Glacier 160 Gaming PC
iBuyPower Gaming PC Element 9320
CyberPower Gamer Xtreme Gaming PC
CyberPower Gamer Master