First what is you budget? Good video card will require power supply upgrade for sure. Without power supply upgrade the best solution would be Sapphire 7750. Would you also consider memory upgrade, if it is possible? And the last question regarding CPU, if it is possible, would you consider upgrading this as well? CPU would have to come from eBay, which is generally ok for processors, or craiglist if you get lucky.
RAM upgrade can be expensive, so please post how many sticks of RAM ou actually have now, also, how many total RAM slots you have (there are 5 different Inspiron 530 models were made).
So, first the most important upgrade is Sapphire 7750 for $100 http://www.newegg.com/Product/ProductList.aspx?Submit=E... if you want RAM upgrade as well, this would be it.
If you want to spend your budget on video card only, you can upgrade power supply and get stronger card for the same money.
So, first choose Sapphire 7750 and many be RAM upgrade, or stronger video card and no RAM upgrade, in the first choice please answer questions about your current RAM and RAM slots.