I guess all hotspot clients are on the same network, say 192.168.1.0/24
First you need to separate the clients by two groups using address lists
It depends on you if you are going to create dynamic address lists or static ones.
Once you have created address lists you can use mangle to assing
different routing mark for each of them.
Here you are almost done, just assing different gateways in the ip - route
using the routing marks from mangle.