That is not a bad idea, and can be a good value. However, I do still recommend spending a little more for a modern system, especially the GPU. That RX 580 is not a bad card, in fact I recommend it to budget conscious people. But if you can afford it, the RTX series are better, and will most likely last you longer before you need to upgrade/build again. Same with the CPU. The Ryzen 3 are great, but for gaming, and regular workloads, as programs tend to lead towards using more cores and threads, the Ryzen 5 will also last longer and run better in more modern programs. The list I put together was based on a $1200 max budget, but you can defiantly get away with spending less for a decent rig, that will just perform a bit worse, and maybe not last quite as long until it become outdated.