building a gaming pc would be a great idea because it runs games better than hp or dell, and it is future proof because they are very upgradeable. I dont know what your price range is but an ideal gaming pc will run form 800 and up to run games like battfield 3, and crysis. but for minecraft, and tf2, and flash games just pop a graphics card in your current computer, and maybe upgrade its ram and you should be in good shape. CPU- i5 2500k, GPU-gtx 560 ti, RAM-8gb gskill, PSU- cooler master, CASE- whatever you want, MOTHERBOARD- lga115 130 dollar mobo or up HARD DRIVE- 1tb sata hard drive. This gaming rig should land you just under 900. Plus if your planning on making a cheap one, then eventually making a good one, i dont recommend it because if you save the money now and buy it all later it will be better than both of the gaming rigs you were planning on doing in the first place.