What are the current specifications for your Dell Optiplex 9010? What games (please be specific - because it helps better determine your situation) are you going to be playing?
Looking up information leads to multiple different configurations. But to answer your question, yes. You can upgrade the RAM and GPU, but you will have limitations. First off, you have a limited wattage on your current power supply (Depending on model, you have one of 7 different power supplies ranging from 200W to 275W). So if you are adding a more powerful graphics card you may not have enough "juice" to run the whole system after installing. You also have a "form factor" chassis. This means that you, can most likely, only fit a Low Profile video card into this computer.