Start by managing your model better by trying to reduce its size as much as possible. Purge it. Save it using compression. Export your families and reduce their size as much as possible then import them back in ( purge them too). Remove linked in DWGS or images etc. Remove redundant content.
$500 is a pretty low budget for a Revit laptop. I would start at $1800. If this is beyond your means, then you should go for a PC as you will get more bang for your buck.
Specifications to be aware of:
1) CPU should be high frequency. Revit only uses one core in the CPU ( except in rendering)
2) RAM should be 16GB min.
3) GPU should be as much as you can afford. Revit prefer's NVidia GPU's but others work too.
The Revit Guy is pretty bang on with this video citing an Origin laptop. ( https://www.youtube.com/watch?v=TuRxn2G4PQw)
I can only recommend a Dell G7 as I have had tremendous success with them. Get one with a Max-Q GPU.
__________I'm the guy they come to when they didn't follow my recommended workflows.__________