Hello,
As mentioned you will get a more rich experience and fully featured SD-WAN using an MX.
However, if all you’ve got is an MS250, I will note one feature you might be able to leverage, which would be ECMP routing.
If both upstream gateways can run OSPF and if they both can advertise a default external route (0.0.0.0/0) to the MS250 with the same cost, the MS250 will load balance traffic to both gateways using ECMP.
It is purely active/active and won’t provide as much flexibility as an MX (nor will it do NAT), but it is a possible configuration to use in a pinch.