There are TONS of references that are out there that offer reference material. ALL of us including me have made mistakes and will continue to do so. The only way anyone is going to get better educated is to visit the sites we give each other and read about it. I cannot begin to tell you how many hours I have spent reading about coins, and looking at pictures. I still do it, even after 35 years+ in the hobby.
I will say point blank is that your confidence in coins will come with time. Coop has a TON of great examples and he is always willing to show them. I think about these coins logically and try my best to assess what is/went wrong with them. Circulated coins are always subject to post mint damage and odds are that most will get
PMD, and at times its real tough to distinguish between what is a variety or error and what is
PMD.
On the other hand, striking out is life. I am blessed that I can afford a good setup and I can buy uncirculated coins. But, I personally find it frustrating at times when I think I see something obvious, and try to offer a point blank answer - I'll try to help on the coins that are questionable, and look promising. I usually don't have a lot of time on this forum, and I have a business to run and a full time job as well. Others will be more than glad to assist on a regular basis, but feel free to bookmark the sites, even these posts for future reference.
I highly suggest taking a look at;
NGC Variety plus. Click on an area of interest. If there is a camera next to the coin description, it should have a HUGE picture of the variety/ error;
http://www.ngccoin.com/vp-categories.aspxwww.coppercoins.com is another site. Look to the top left for die search. Put in the year in the top box. Leave the 2nd box "until" blank. Check the box whether it is a P, D or S and hit go.
John Wexler also has a LOT of data about coins, errors and coins that look like varieties but are not. Some of his descriptions go to the brink of extreme to try and document what went on, which is some commitment to the community.
http://doubleddie.com/There are a ton of other sites, depending on the coin type.