I sell full time on
ebay, but nothing related to coins. So my advice may not line up 100% with what you are doing, but in many ways
ebay is the same no matter what you sell.
First class is the way to go as it is far and away the cheapest way to ship. I wouldn't worry about insurance unless you are selling a higher end item. I've made literally thousands of sales and a package has never gone permanently missing. Delays are very common, but not missing items. The only case where the item may have gone missing is someone that claimed he didn't get the package even though it said delivered. He was probably telling the truth, but regardless the USPS wouldn't have paid for that even if I had insurance as they will claim they delivered it. If you ever get a negative review do not respond angrily. Make a level headed response that makes you look like a professional and the buyer unreasonable, or own up to a mistake if you did something wrong.
You absolutely should print labels at home. No serious seller waits in line and pays full price at the post office. Plus you'd have to upload the tracking number by hand that way. It is super easy to ship with
ebay. When you have a sale just click on "print shipping label" link. Then pack the item but don't seal it up yet. Weigh the package, select the weight (always round up, for example 2.1 oz is 3 oz for shipping purposes). It will then make a label you can print out and stick on the package with tape. You will probably have to adjust the size in your print settings until you find the label size that fits your package the best. I always print out a packing slip too as it makes it clear to the buyer what they received (some people buy lots of stuff and forget what's what). Plus it has your and his address, so if something happens to the label the post office can open it up and find out where to send it.
Be as honest as possible about what you are selling and learn to take good pictures. If people can see the item clearly and you tell them about an issue you are aware of (such as cleaning) they are far less likely to return it. Yes there are plenty of horror stories of bad buyers, but most people are reasonable if they feel you were honest with them. If you do have a problem buyer don't get angry with them. Negative ratings can really hurt you, especially when you don't have a ton of positive reviews to balance it out. Sometimes you just have to give them what they want to avoid a negative then just block them.
If you do auctions be sure to time them so they end in the evening, with Sunday being maybe the best day. That is when the most people are on
ebay so your odds of more bids will increase. That being said, I moved away from auctions a long time ago and only do buy it now except in rare cases. People like to buy an item right now, not wait for a week to see if they get outbid. If you have something genuinely special that is rarely seen on
ebay then an auction might make sense.
Always keep some money in Paypal. How much depends on how much you sell. I like to keep $500 minimum, but I sell thousands of dollars of merchandise per month. If you are making a small number of sales then $50 is good, but make sure there is always enough to pay
ebay's bill at the end of the month. They deduct it automatically so be prepared.
I'm happy to answer any other questions you might have. Congrats on your first sale by the way. I hope you keep having success!