I’ve skinny fingers, and I have a couple of rings that I really like but they're too lose. Is there something I can do to them or purchase to put on them to make them tighter? Without paying a lot of money to get them fixed by a professional jewelry person.

Answer:
You can purchase a pack of clear ring guards from a department store (preferably Kmart because I use to work there-hehe) for $2.99. The quantity of each pack is around six or so. You can find them next to the costume jewelry (the fake jewelry). The slide right onto the back of the ring. (They won't fit on really wide rings.)
Answer:
They make ring inserts that you can just purchase at walmart. Usually you can get a cheap pack of different sizes. Theyre clear and just slip on the band of your ring under your finger and make it tighter. Hope this helps : )
Answer:
You can take them to a jeweler to get them re-sized.

And in the future, make sure you find out what your ring size is and purchase rings that fit.

Answer:
Get a piece of thread and use on it, very cheap