If money is tight I would get the exhaust sorted first, then save up again for the remap, as you should have the remap done after engine mods to get the best out of it. If you had it remapped then changed the exhaust you would not get the full benefit of the exhaust until you had a remap again.
All engine mods go hand in hand, they are all a balance, and imo you should make the remap one of the last ones if you have finished the mechanical mods for a while. Don't have a remap and then go and change a load of bits as the remap sets the car up with whatever it has at the time.