Yes, it is ok for gaming at the 1366x768 resolution. And no, it is not at the bottom of the gaming heap. It is somewhere in the middle of the heap.
For the mid budget, you have very good laptop that has enough power to play nearly all modern games. Some games are obscenely demanding nowadays (Assassin's Creed Unity, Ryse: Son of Rome etc.) and will not play on high or even medium settings on any laptop priced below $2000.
Here's a link that you may find useful that has all the gaming benchmarks for your GPU
http/www.notebookcheck.net/NVIDIA-GeForce-840M.105681.0.html
Hope this answers your question.