Have a good look around. Email and ask questions. I had planned to buy a lot of stuff from one guy, bought one item and asked some questions about another. He was so unhelpful with following up the questions, so arrogant, so rude I didn't buy anything else from him. As an example, I asked him the post on XX items, he told me to buy them and he would work it out. That sort of rubbish

Not a "bad" seller either. So ask questions, see how you feel. If they are unhelpful or rude then buy from someone else. anyone who is rude before you buy will be far worse after
Search worldwide AND on the local searches for OS. Not everything is listed on WW search even if it should. I have been able to demonstrate the SAME search from two different IP's give different results, one had a lot more items.
Check what you are buying with local prices. SRAM shifters can be had cheaper locally for me than Ebay, yet chains are much more expensive.
Watch was it actually said in the auction. "Like new" is not new

Read everything a few times. Get insurance, read up on how ebay will act if you have an issue. Not likely to get all your money back

Can you afford to lose what you have bought? There are people who scam and ebay often does not protect the buyer.
I use my CC linked to paypal. I EXPECT to have an issue one day and to do a charge back the second Ebay are unhelpful

I would lose my account.
Pay close attention to post. Ask before you bid. Watch out for seconds. Carbon fibre gear is well known for this on ebay. Remember, no local warrenty. Often no real warrenty at all (mind you, lots of guys are let down buy local retailers anyway).
I have found some really decent sellers. One guy ordered me stuff in. under 40% of the local price to my door. Just take your time, don't rush
"We" have a lot to gain and little to lose by shopping on ebay. My local bike retailers are a joke. They really are. Was looking in one today for a part. He didn't have any in stock and I was not sure what he could get in was what I wanted. The two Mechs were talking about it and the owner was pushing me out so I would go. None of them were busy. We were not wasting time but talking about the part I was looking to buy.
Another larger retailer ordered some shoes in for me to try. Didn't ring when they were in and when I rang to follow up was told they were in stock. Went and looked and they had got the wrong part in. The owner told me to try these other ones as I would find some he had in stock. Which I had already spent time doing
Or the time I went to buy some Raceface pants (legs getting cut up by bushes). Not one store had ANY in, not just that brand but ANY. Of course they would order me some but it would cost 1/3 -1/2 to buy them from OS
So, Ebay can be good but you need to take care

You have no protection over here with them. no legal cover
