Honestly, budget PC and DCS (or sims in general) don't really go together IMO. You can get away with using an older CPU, but VRAM is a must. Especially if you are considering VR. Personally, I wouldn't get a card with less than 16GB VRAM. 24GB if you are planning to go VR. Despite sims becoming more optimized, they are also becoming more intensive and you don't want to be upgrading GPUs every release cycle.