First of all, welcome to DPF!
You will have a blast here!
When I buy from eBay sellers I look at multiple things. The first thing I look at is feedback score and check to see if any neutrals or negatives are from complaints of scrappers. In fact, if I'm buying an extra expensive pin, I wont even touch anyone with a neutral or negative feedback regardless of the reason (unless I know them/have dealt in the past). Then I check out the photo of the pin, and I make sure it's not a stock photo or something pulled off of PinPics or the front page of Google image search. I want the photos to be of the ACTUAL PIN I'M RECEIVING! Then, I check out as many sources as I can for information on possible scrapper alerts on that pin, and I also compare photos of the known genuine pin to the photos of the eBay listing for all of the fine details. Color differences, less-defined lines, etc.. If it's an expensive pin I also try to get them in original packaging as a bonus. If I feel like the photos are too blurry or I want to see more/the back, I would contact the seller for more information. If everything checks out to me, I'll buy the pin and wait to leave feedback until I've inspected it in person. I've purposefully bought a scrapper pin before as a way to compare some fakes to real ones more easily in person. There are a lot of guides on signs of scrappers/fakes, but I really do find that having a couple of fakes on hand to compare with helps me a lot.
Anyway, depending on what types of pins you are collecting, some are more prone to being scrapped than others.
Also, I second what Speed said! Most of us here are either serious collectors/traders or just really helpful and fun people in general, and you can always ask for advice or post photos to ask for help inspecting a pin as well! You just can't post links to eBay listings directly. I think private messages are okay.