I would recommend you League of Legends. Almost everyone that tried League of Legends liked it. Even those who are RPG and FPS players. Furthermore, it's very graphically light but eye pleasing. Even a non-gaming PC can run League of Legends at a more than playable FPS. And on an entry level gaming PC, it would run 100+ FPS at 1080p max settings. The only downside is, although it's free to download, in-game purchases are irresistible as it will make you even more happy. But if you choose not to spend a single cent on the game, it's fine, your gameplay will still be fair as real money does not affect character powers.