Just a bit of advice before you catch auction fever and go broke buying vintage parts.
If there is a particular part that you have decided on, observe what the prices are that they are actually selling for. Just because someone lists something for a high price, doesn't mean that it is worth that much. Actual selling prices are often much lower so check some completed listings or ask around for advice on what to pay for something before you get cheated.
Don't get caught up in bidding wars. If someone outbids you and you aren't sure you should make another bid then drop out. There is no feeling worse than getting a part and finding out later that you could have gotten it for less.
Watch out for sellers charging high shipping to avoid paying ebay fees. That BIN price may seem like a bargain but if the seller is charging a ridiculous amount for shipping, it's not a bargain anymore.
On the subject of bargains, if you know a part normally sells for more than what a particular seller is asking and you want that part, then buy it quickly before someone else does. In the time it takes you to ask the seller a question and get a reply back or for you to make up your mind whether to pull the trigger on that low BIN price or not, someone else will have it and you'll miss out. This is a highly competitive hobby when it comes to acquiring rare parts for cheap.
Try to get a feel for the rarity of a particular item you want. If a part comes up only once in a blue moon then you have to decide whether it is worth waiting if you let it go or if it's better to pay a little more now just to save yourself from waiting years for the next one. Sometimes you just have to reach a little deeper into your pocket for the especially rare item that you won't see again for years, if ever. Don't go mad, though. Overpaying a little is sometimes OK if it means saving a long wait, massively overpaying usually isn't.
Try to get a feel for who the good sellers are and the bad ones, too. Everyone here and on other forums has sellers they deal with on a regular basis for being good sellers but we also have horror stories about the bad ones so checking if anyone has any info on a particular seller is always a good idea before you get jerked around.
So educate yourself a little and you'll be able to build up a nice collection without being ripped off.