Have a look at https://github.com/barryvdh/laravel-debugbar.
It has details about the memory utilisation or try telescope (it's head and awesome!)
This will give you an idea of usage per request and also give you insights into where any performance issues lie e.g. n+1 queries.
Once your happy with a single request you can load test with something Iike siege
http://lifewithlaravel.blogspot.com/2016/08/laravel-load-testing-with-siege.html