There are many cheaper parts you can invest in that'll give you a high quality computer. There are parts I would avoid, however, such as an SSD. Parts like this won't enhance your actual gameplay (minus loading time) and will bump the cost of your system up $100+.
Follow CompulsiveBuilder's suggestion of referring to "Tom's Guide (...)" so you can get a base understanding of what you're doing. Post in the Systems section for questions about your build. Good luck