This is a bit more technical but I've been there, bought the T-shirt, and don't think I'd do it again.
In all seriousness, you could easily purchase a very nice microphone for the cost and time to put together a gold coater - you won't save any money and you'll probably just get frustrated. Then you'll be having to look for a mental hospital. Unless you're really determined to figure it out.
It took me many weeks (maybe a few months?) to get my coater to work - lots of vacuum leaks. And you can't find them easily, a leak can let in literally a few atoms per second of air and that ruins the process. Your vacuum system needs to maintain better than one micron of vacuum - lower leads to less contamination of the gold. That is a pretty hard vacuum, you use a diffusion pump to achieve it. Very few mechanical pumps are capable down there. Actually, you use a mechanical pump to rough-pump the chamber down, and another mechanical pump to 'back' the diffusion pump. If you're interested, look up 'thermal evaporator' on your favorite search engine. I would never recommend to anybody to DIY that project unless you really have to, having done it. My setup cost me at least $2500, using mostly ebay bits. The oil for the diffusion vacuum pump was around $100.
If you do decide to build a vacuum coater, one wrong valve move will make a mess that takes several days to clean up. I now use a programmble logic controller (with safety vacuum switches) to ensure proper sequencing of roughing-pumpdown-deposit-cool-vent cycling.
As a DIY, I'd follow Tim's recommendation. That limits you to edge-terminated capsules but that's fine. There are plenty of edge designs out there. The Stebbings/Debenham/Robinson capsule is quite nice, and it has very good machining instructions. They may seem terse if you're not used to machining - they assume you know something about using a lathe and a mill.