Whether you're selling gold coins, jewelry, or bars, it's critical to find a good buyer. There are a ton of businesses that trade in gold, and they're definitely not all created equally.
Frequently the value of a gold item is at least partially subjective, with things like rarity, craftsmanship, and other factors heavily influencing the value. It's important to go into any potential selling situation well informed to help you get the best price!
Whether you decide to go with a national service where your items are mailed in and appraised, or a dealer local to Vienna, research is key. Know who you're dealing with by checking with organizaions like the BBB, and know the value of your items by checking spot prices and getting competing offers.
Selling gold can be intimidating at first for a new-comer, but it doesn't have to be! As with all things in life, preperation is the key to success.
As a general rule, you should look at buying legal tender gold coins wherever possible. This will almost certainly include less overhead and premium than other formats, and be closer to the true spot price of gold.
Purchasing rare gold coins should be avoided unless you really know what you're doing. Some subjective measures of value are easy to misjudge, and may result in you getting taken advantage of.
Governments around the world have seized noble metals from time to time, so keeping your entire stash locally could be a bad idea depending on where you live.
Safe jurisdictions like Switzerland should be considered when you get to the point of holding a significant (tens of thousands of dollars worth generally) amount.
Buying gold on credit or speculating on the future price can lead to getting yourself in a significant financial jam.
Instead, put some money to the side that you're sure you're not going to need in a short time horizon, and use that to invest.
Physical precious metals like gold are a hedge to the traditional banking system. In a crisis, if the system collapses, it may very well take your property down with it (if it can).
If there is a run on the banks, having your gold under your direct control means they can't confiscate it, block access to it, or have loaned it out in a leveraged fashion.