Start small, but with a good foundation for expansion. Unless you have the cash to invest in many, many GPUs that will be outdated in a few short years. While you still might be learning the ropes.
Buy a good mother board that supports many PCI-express cards. Buy a modest CPU. A fair amount of RAM. The thing you want to focus your purchasing power is GPUs and an efficient power supply. You won't need much of a CPU or much RAM for a mining rig. A good power supply is wise also. Get one that is "gold rated". This means it is more efficient at converting AC into DC than say a "bronze rated". Thus wasting less electricity in the conversion.
Forget the fancy and pricy computer case. Get a milk crate. Open air is what you will need, not a cramped box.
I do not have any extra GPUs but, I do have an extra asrock pro BTC H81 I would be willing to part with. This is a motherboard built for GPU mining. 6 PCI-express ports means you can run up to 6 GPUs but, you would need two power supplies to do that. I run 3 gpus off of one 1000 watt corsair PSU and it doesent even grunt. The motherboard is unused and in the original packaging. I can kick in a couple free risers also to help an up and coming miner. Risers are just cables that alow you to plug the gpus in away from the motherboard and other gpus. Aiding heat dissipation and making room for airflow.
Of course I would make a sweet deal for a BERN supporter. I bought the motherboards bulk and saved. I have no problem passing that savings on to a fellow berner.
You would need: a power supply (preferably gold rated ~200$), a CPU (I used a socket compatable pentium, 40-50$), some RAM (8 gigs ddr3, 60$), a hard drive (ssd have dropped a lot but, even an old HDD will work fine), milk crate (take one from a gas station), and then, the important part, GPUs. I recommend shopping around on crypto marketplaces like cryptopia has. I literally STOLE a R9 280x ($200) for 14$ worth of bumbacoin once. You can run ubuntu instead of windows for more savings. Of course, if you can afford to not take the finacial shortcuts I suggest, congrats.
Anyway, let me know if interested. PM me where I would need to ship the mobo (motherboard) and riser cables and I will figure out a price. Basically, I would just be justifying the shipping. I am not using the mobo and know you have helped BERN a lot. Scratch my back, I scratch yours.
Mining is an addiction. If you have a wife, tell her I appoligize.