Hi Mike:
Good Luck on your venture!
We have 14 different eBay user id's - three of which are Silver Powersellers...it's a lot of hard work, but we love being able to work from the home and spend time with our children.
My advice would be:
Treat your customers right, and treat your repeat customers like gold.
Offer discounts if possible on multiple purchases
and
Utilize the Second Chance feature (this would work great for what you sell, if you have duplicate games!)
Also, Don't take Negative Feedback too seriously!!!
All the Best,
Jamie