Yes, you can enchant rings with a specific purpose. You can use this ring to draw in a energy, like an energy for healing or love. You can also enchant the ring with the intent of protecting you or guarding you from something, like negative energies or even positive ones because if you draw in too much energy, you may become unbalanced to the point where you might have to cleanse or ground yourself. Your enchanted ring can be any, plastic, metal, real or fake. To enchant a ring you can simply hold it in your hand while thinking of your intention thoroughly. You may say a spell, but it is not needed. A suggesting would be to cleanse the ring to get rid of leftover energy and consecrate the ring to bless it, then proceed with your enchanting. Be forewarned that enchanting wears off after a while.
I hope this helps.
Yes, you can enchant any ring you desire to do anything you desire, but most people on here will be more familiar if you use the term charging rather than enchanting. We tend to trend towards separating ourselves as far as possible from the magic in the media.
Charging requires a bit more than holding a ring and having your intention in mind. While that can charge it, it will be less successful than if you actually charge the ring with that intent intentionally. You can do this with a spell, as Seeked said, however you can do it simply if you hold it in your hand, form your energy with your intention, and push or attach your energy into the ring.
There are limitations to this, as there are to all things in magic; it won't make you fly, it won't stop a bullet, etc. However, it can increase your luck, bring love into your life, ground you, make you feel better when ill, etc. I used to use three rings specifically in this way, as it allowed me to ground out negative energies more easily (I have never found "traditional" grounding easy). However, I stopped after I cracked the stone in one of the rings when I clapped my hands together. It could've been just a coincidence, but I would rather be safe than sorry. For the last few years since then, I've found a better way for me.
If you give more specifics about what you want the ring to be used for, I would be more able to give you instruction on how to make it more successful.
For luck or increased strength, you could use herbs, and put it under the light of the full moon to charge it, then wear it after. You can also simply put your energy into the ring, and have it increase your luck. You can also use candles and their colors to further will your working into being. All the mentioned above are tools, they increase your own ability to charge the ring and to make it more successful. If you work with direct magic or energy flow and control a lot, you will not necessarily need these to get the ring to work successfully, though they certainly help regardless and make your job easier.
The increased strength part won't make you actually able to lift more than you actually can, but it will "unlock" for a better word, the potential that you do not normally use. This potential is what allows mothers to move a car off of their children when in an accident. We do not use our muscles to their full potential often.