It's best to first identify what type of skin you have. Are you dry, oily, combination, or sensitive? You'll need to know this first as you may have skin concerns that you'll want your skincare products to address.
Now it's time to build your skincare routine.
You'll do with just a cleanser or moisturizer or you can go with the whole Korean 10-step skincare routine. It depends on your skin issues and things you want to address so you can build up form there.
Here's some essential things you'll want to get:
Gentle face cleanser
Other things you may want to add:
Spot treatment cream for acne
Serum for addressing certain skin issues
This is not really a comprehensive guide, but it should give you an idea.