i3-4130/4160/4170 mainly for gaming.
AMD FX-6300 would be best for multitasking and using multiple programs.
Both costs just around as much.
For gpu, you can't really fit anything good in the budget.
i3/FX-6300 = 100$
cheapest motherboard for one of them = 50$
With 300-350$ budget, you might be able to fit GTX950.
At the least GTX750Ti.
Do you have DDR3 memory already? If not, then you will need it as well, which costs at least 40$.
At the very least, you will need 350$ as budget for anything decent. Preferably 400$.