Thread balls up in the bobbin/singer sewing machine, also thread

Nesting of thread on wrong side (bottom) is usually top thread tension too low.

To be sure which thread is nesting try test sew with different color top thread.

If its bobbin thread then theres likely a problem with bobbin thread tension. Check the bobbin thread has not escaped the tension spring.

Try following link

https://www.singer.com/troubleshooting-tips

Serger Help

1. Place spool of thread on spool pin. ...
2. Pass thread end, from inside, through the small hole in the rim of the bobbin (illustration 2).
3. Place bobbin onto the pin. ...
4. Holding thread end, step on speed controller to run the machine until the desired amount of thread is wound. ...
5. Trim thread ends from top of the bobbin.

https://www.singer.com/sewing-resources/winding-a-bobbin-alt
Machine will not pick up bobbin thread. ... - Your thread could be caught on something between the needle and your spool of thread if so, your thread will be too tight for the needle to pick up the bobbin thread. - Make sure that the upper thread is threaded properly. - Re-thread your machine, if necessary.
https://help.brother-usa.com/app/answers/detail/a_id/76369/~/machine-will-not-pick-up-bobbin-thread

Bobbin Tension How and Why Tension is Adjusted

Understanding Bobbin Tension

Understanding Thread Tension Threads

Sewing Lesson 10 How to Fix Tension on Your Sewing Machine

The needle thread breaks
1. The needle thread is not threaded properly
2. The needle thread tension is too tight
3.the needle is bent or blunt
4. The needle is incorrectly inserted into the needle holder
5. The needle thread and the bobbin thread are not set under the presser foot when starting sewing
6. The threads were not drawn to the rear after sewing
7. The thread is either too heavy or too fine for the needle

You can buy a copy of the manual. Ebay has one just now. http://www.ebay.com/itm/SINGER-SEWING-MACHINE-OWNERS-MANUAL-MODEL-3014-REPRINT-/380168853967

If you enter the model number and make into google, you will find other sources for manuals as well. Most Singers are not hard to thread, but some of the older ones have a few quirks. Get a manual so you can make sure you've got it right.

Sewing machine basics are whenever you have thread balling up, you stop, clean all lint from around the bobbin case and feed dogs, check all the guides to make sure none have any damage, put in a new needle, in case the old one has a small burr or other damage, and rethread the machine. Then turn the hand wheel slowly and watch the thread move, to see if it's catching anywhere.

Also check the upper thread tension, because if it is too tight or too loose it can cause a lot of problems. And lint buildup around the bobbin is often the cause of bobbin problems.

try changing the needle
rethread the machine top & bobbin
check to see if the thread has come off the thread take up lever
clean under the needle plate & in the bobbin area for lint & thread

Think in opposites... the top stitch is formed by the bottom thread tension and the bottom of the stitch by the top. So either the bobbin thread is too tight or the top thread is too loose. Check the bobbin thread first as that is the one most overlook. It should come out of the bobbin without having to yank it hard but it should have a little resistance.

Recheck the top thread and bobbin tension for equal balance of thread when sewing. The knotting of thread problem is usually because the tensions are too tight or too loose and/or thread may not be properly threaded. Another reason is when the bobbin thread is wind imbalanced it will cause the thread to knot-up when sewing. This problem is notorious when the bobbin is winded within the bobbin case on some machines. The bobbin thread need to be wind smoothly in the bobbin to avoid this problem.

Start right from the beginning, make sure the presser foot is up when you thread the machine, make sure the presser foot is up, top tension should be about 4 or 5, make sure you use a good mercerised thread, make sure the bobbin tension is not too tight, you should only be able to pull the thread through with slight resistence, if it is too tight slacken the large screw on the bobbin case about a quarter of a tutn at a time and test.

I am not sure about this particular machine but in most machines there will be a nob on the front loose low numbers like 0 1 -2 work well on number 3. If the nob is not on the front check and see if it is on the side.