Jewelry care is really important when wanting longevity of the item. Silver jewelry tends to oxidize over time. It happens because of a variety of factors, including sulfur, sweat and elements in the air. To protect your jewelry from oxidizing too fast, the best you can do is store them right. 

Each ILONA jewel is shipped with a little plastic zip bag, laying under the foam in the box. It is highly advised to store your jewelry in the bag or something similar whenever you are not wearing them. This will keep out dirt, sulfur and air, so that your jewelry doesn't oxidize as quickly. 
If your jewelry has oxidized, the best tool to clean them is the Hagerty Silver Clean. It is easy to use and can be used very gently on gold plated silver jewelry as well. 

Applicable for all jewelry is to take good care of them by not wearing them when you shower, sleep or work out. 
If you follow these guidelines and care for your jewelry, they can look bright and shiny for many years to come.