I will be explaining do's and dont's when buying on eBay out of my own experience.

Dont,s

1.-Do not bid on random lots or "x card 50%" lots

   - It,s both unsafe and illegal on eBay.

   -you will never get what you want

   -you will not get your money worth of cards

2.-Do not bid on "winner will get 1 of these 4 card lots"

   -ex: winner will get 1 of these 4 : 1-dark armed dragon 2-crush card virus 3-i'll blud  4-felgrand dragon

    on this lots the seller will only send the cheapest card on the lot, even if the auction goes over 1000, 

    this means that for this lot the seller will send 4 felgrand dragon the winners instead of the cards on the list.

   -even with the new feedback system, you will end up to pay 20 to 50 dls, in some cases even more

    for a card not even worth a buck.

3- Be careful with 0 feedback for in multiple ocassions I had bid on 0 feedback members and soon after I pay they become unregistered users, and even though I got my money back most of the time, it took a lot of time.

do's 

1- It is always safe to buy from members with high feedback, but check the DSR's for the shipping time,

usually a full 5 is good, but with members with 1000,s of stars a 4.9 or 4.8 is terrible.

2-Usually members with an eBay store are good sellers and buyers