For everyday and casual purposes, I usually don't wear earrings if I'm wearing a necklace. Wearing both feels like too much for my casual elegant style.
If dressing up, I might wear earrings as well as necklace. Usually not matching sets (except pearls) but I want them to look harmonious, so same material or colour will be fine. If the earrings are big, I will wear a simple necklace. If wearing a statement necklace, I will wear simple earrings.
I am tall-ish and have a big nose, big ears and thick wavy hair. Tiny earrings don't work for me. Mine need to be medium or big. It's a matter of proportions.
Silver or white pearls echo my silver white-grey hair and go with everything in my wardrobe. However, I also like to wear fun colours--and materials like enamel and polished wood. When wearing coloured earrings, I want to repeat the dominating colour somewhere else in my outfit.
I often wear reading glasses, and I don't mind wearing earrings and glasses in different colours or materials. However, I always make sure that non-neutral colours worn so close to my face are repeated somewhere else in my outfit. (Example: Let's say I'm wearing red glasses and cobalt blue & silver earrings. Then I might wear red shoes or a red cardigan plus a blue skirt or a blue top. Or a patterned scarf including red and blue.)