Computer build questions

So, I've been approached about working on a project for the summer in Unreal Engine 4. The problem is, my current rig is basically a toaster, and building anything takes hours. I've been considering upgrading my rig for a while, but this project changes the constraints of my planned build, so rather than being a gaming rig it also might need to be able to do lighting and stuff. I was wondering if any of you all had any advice on my build; I've started one, but I don't know what is best for doing stuff in Unreal, so if anyone has any suggestions for alterations to make it work better for working with UE4 (I'll mostly be doing some level design and reviewing builds made by the more code savvy people, but I may be involved with cutscenes and stuff, since our team has no dedicated artists and I'm consulting on writing and design). The budget is fairly tight, and anywhere anything can be trimmed without sacrificing would be appreciated. The point I insist on is RAM (need 16 GB), but anything else I'm open to suggestions. Thanks!