eBay feedback score is a very important part of your reputation as a buyer and a seller. The higher the score, the better your reputation. The only piece of advice I can give for building your feedback score quickly is simply to purchase low price items. So, go for items priced between $.01 - $5.00; with or without delivery and you can typically build your score and reputation relatively quickly. Be sure to leave your seller positive feedback; and if they fail to to the same quickly - just ask.
Happy buying and selling,