Corssfire is used most with very high(more performance then many need) or mid end(2 x mid end cards on sale can many times beat a single higher end card on price and performance) cards.
that part aside, you also need a crossfire ready board. So we need more specs.
@ $30 you are not getting 2 of anything. It will be very hard to get a good card in that price range.
For instance you can get a 8400GS for $30, but it is SLOWER then your card.
You are best to lower in game settings and save up some more. even $50 was a tight budget for gaming.
What kind of specs do you need?
(For future reference.)