I've been selling on and off (ie not professionally, but a lot of personal possessions and listing for family and friends) for about ten years so I can offer some advice for ya...
- eBay charges 10% on pretty much everything (I think eBay Motors might have a different fee structure, but don't quote me on that).
- eBay also charges 10% on whatever you charge your buyer for shipping. This was done to encourage sellers to offer free shipping. And frankly, I almost always just up the initial price of the item to cover shipping so that I can put the "Free Shipping" on the listing. You'd think people would be smart enough not to fall for a gimmick like that, particularly when you can search for lowest total price, but apparently they aren't. I've done both and even when the total price for the buyer works out to the same amount, listing something with "Free Shipping" has a much higher successful sales rate. Although, I will include a shipping charge on heavy objects, but, in such and instance, always state how much the item weighs in the listing so that a buyer can't claim overcharging.
- Paypal charges $0.30 + 2.9% per transaction. You pretty much have to accept paypal to sell on eBay unless you're a power seller/merchant that's set up to accept direct credit card payments.
- Be thorough and honest in your listing. I can't not stress this enough. Most seller vs buyer disputes happen because a seller wasn't honest about the item condition. This is particularly important when it comes to anything of the collectible variety. If there is any major flaws, make sure to state them specifically.
- Picture, pictures, picture. Take lots. You get twelve pictures for free with any listing. Use however many of those twelve you need to in order to physically show all relevant sides of an item. For something like an Amiibo, takes pictures from the front, back, top, bottom, and both sides. Also take specific pictures of any damage (ie there's a bent corner on the figure's card, take a close up of that). When it comes things like music, movies, games, and books eBay has a system for an easy listing with item details and a stock photo. Never use the stock photo. Delete it and use your own. Not only does this show the buyer the actual item they're buying, but it helps your listing stand out from the flood of stock photos.
- Create a write up with general transaction details that's included in every listing you make. This has saved me from many disputes and buyer/seller confusion. I have one I'd be happy to send you via PM if you'd like an example, just let me know. Basically, you just want to outline things such as the payment and shipping timeline, whether or not you're willing to ship internationally, and any other pertinent details that generally relate to anything you might be selling.
- As far as pricing goes. Research. eBay has an advanced search option that allows you to see only completed or only sold listings. Use this to gauge what your item typically sells for and price it accordingly (though keeping in mind shipping costs if you choose to go with the free shipping option). Nothing will kill your sale faster than an overpriced item. On the flip side, nothing will kill your profits faster than an underpriced one.
- Seven day auctions are generally more successful than anything else. Though, I do something run three day auctions as well.
- If selling via auction, set your listings to end on either a Sunday, Tuesday, or Wednesday night sometime between 9:30pm and 11:00pm eastern US time. This isn't really a hard and fast rule. Just something I generally recommend based on my own past experience. Things I've sold via auction ending on those days and times are generally more successful than any others. And you can set your listing to begin at a specific time, so you don't need to make sure you're online, listing things exactly seven days before you want it to end.
- On the flip side, you can list things via Buy It Now instead of auctions. Honestly, I do find that the percentage of non-paying buyers is much lower when going this route (especially if you click the 'require immediate payment on buy it now' box). You can add a Buy It Now price to an auction listing as well and it usually won't cost any extra. Alternatively, you can just go Buy It Now with a Best Offer option as well. That allows buyer to either buy it out right at the stated price or send you and offer to consider. And you can set the listing to automatically accept or decline certain price points to avoid having to field a ton of low ball offers.
- On selling single items vs selling in lots... It really depends on the item. As a general rule, anything that's a bit more rare or sought after, I would sell individually. Anything that's pretty common and easy to find either in store or online, I tend to sell in lots. Again, this is particularly true with anything of the collectible nature. Reason being is that if you're going to get a buyer for the common stuff, they'll generally be someone just starting out, so they'll like the idea of having a nice little bundle to start with. Whereas the rarer pieces are probably going to bought by someone looking for that specific piece.
- Lastly, keep in mind that you may encounter the negative aspects of selling on eBay such as non-paying buyers, questions that are easily answered in the listing, upset buyers, and so on. There are a lot of horror stories about selling on eBay out there. Some people will try to tell you it's the worst thing in the world. It can be, yes. And yes, I do believe that eBay charges too much to their sellers as far as fees go. However, there is literally no other site with the vast reach of eBay. Selling on there allows you to basically have the entire world as potential buyers if you want. More importantly, as long as you're smart about it and take measures to protect yourself as a seller, you won't have too much trouble. I've had pretty much everything happen to me at one time or another as a seller over the years. But, I regard my experiences as far more positive than negative.