Quite a good budget actually, try for APU in this case

AMD A8 6600K blk (HD8570) RM429
Asus FM2 A55M-E RM229
Kingston value RAM 1600Mhz 8GB RM229

Total RM887

should be able to play more thna DOTA with this spec, the built-in GPU should be plenty of an upgrade in comparison to your current setup, should be able to play quite a number of games in mid quality settings

http://www.xbitlabs.com/articles/cpu/displ...well-gpu_5.html