So i know that ideally i'd need to cover all corners with bass traps but currently i can only afford to get two, so where would be the best place to put them for mixing, so for example in the corners behind the monitors or in front?
In the corners to your front right/left when facing the mixing board/monitors.

If you're buying from retail, you're getting ripped off. You're MUCH better off building your own, it works out to about $15-30 per trap depending on materials. There are a million threads on this forum (and others) that detail the process. I'd recommend spending some time reading up on that.
Telecaster - SG - Jaguar
Princeton Reverb, Extra Reverb
P-Bass - Mustang Bass
Apogee Duet 2 - Ableton Suite