New To Paper Money. What Is Collectible ?

Just like coins, the value is in the condition. A beat up silver certificate from circulation isn't worth nearly as much as a crisp circulated version of the same note.

Star Notes: These notes are worth more over time. You may have seen them and not noticed, but in the serial number either at the end (modern notes) or beginning (silver certificates) there is a 5 pointed star. These bills are also called replacement notes, and they were used by the Federal Reserve in place of another bill damaged during production. It makes it so that even if there are bills that don't pass quality control, then they put a Star Note in it's place so that over the course of 1000 serial numbers there are 1000 dollars. etc. You can google star notes, and find out a ton of information about them. And in most price guides it will list two prices for each year and denomination. 1963, 1963*, 1988, 1988*. The more time passes (generally) the more the star notes become worth.

WWII Emergency Currency: During WWII the US started printing two new types of currency for Americans in Hawaii and North Africa just in case the areas were captured during war so that US currency wouldn't slip into the hands of our enemies. So the Hawaii Silver Certificates, Series 1935A, had a brown seal instead of the normal blue and the word HAWAII in large letters across the back, and twice in small letters on the front of the note. In North Africa they had a Yellow Seal but didn't have any extra text printed on them. These can be searched as well "HAWAII SILVER CERTIFICATE" or "WW2 Silver Certificate" etc. The values of these vary again by condition and star notes. I think it's the $5 Star Notes that are worth the big bucks if I remember right.

Lastly, (for now), one of my favorite currency rabbit holes to go down is the Series 1929 National Currency. The values of these can seem crazy, but like anything it's all supply and demand. The US had just switched to smaller sized notes we use today, and each bank had currency printed with their town and bank name on it. (I think they might have personally backed the money at the time but I am not sure) But you can search almost any town, or city in the US and find money printed from these series' with local ties.

Some people like "fancy" serial numbers, like low numbers, all the same numbers, or numbers that have a certain kind of symmetry, like reading the same backwards and forwards (radar) or the same upside down, or "birthday" numbers, where the serial number can be read as a date.

Cleatis87, it sounds like you are specifically collecting notes out of circulation, is that correct? If so, here are a few things you are likely to encounter:

Steer clear of star notes in less than mint condition. There's very little resale value.
Spend star notes in denominations over $10. It's not worth tying up your money in high denominations.
It's easy to get caught up in the serial number patterns (different types mentioned above). But unless the number is *exactly* a radar (i.e., 38483) or a *exactly* a ladder (i.e., 87654) then it's an "almost." Spend it without a second thought.
Notes that are somewhat off-center or have a few specks of extra ink are *not* considered error notes. If you find an error note in circulation it will be very obvious.

Just my opinion, of course, but there are hundreds of posts on all the paper money boards with questions like these. Better to learn early.