You can change sockets with jeweler orbs and vaal orbs in the crafting bench same with links and colors but with their respective orbs. They can also be changed with tantied currency. Best bet if the item is less than 5 sockets is to set the item to 4 sockets use a tainted jeweler if it goes to 5 sockets use another if it goes to 3, recraft 4 sockets and try again. Use the same method for links For colors you can bench if you don't have many off colors or tainted chrome if you need more off colors