Let me reinforce the kitten harness idea. Later we found some others that were actually for dogs, but not until our babies had a few more ounces on their little selves. You are going to buy too much stuff--just get happy about it.
Many of your decisions will be made by the "life" you plan for your new baby. We do potty pads, and I have bought holders, cloth potty pads, disposables, and used all from time to time. We live too close to major wooded areas to let such small dogs outside alone, and I prefer cleaning up potty pads to the grass, leaves, and debris that they track in from outside. Others love taking long walks with their pups, and blessings on each and every one.
We have a crate, a gate, a folding "playpen", a small travel crate, a stroller, multiple food dishes, sweaters, harnesses, leashes, toys. . .you get the idea. It is fun to shop before the "baby" arrives, but if you can borrow or make do at first you will save a FORTUNE!
Congratulations on your new one!