Shower caddies and soap holders are a great addition to an existing shower. There are types with adhesive that stick on, which can work, but have unknown durability and others that mount with screws to a tiled wall.
The part people sometimes find intimidating is mounting them to a wall with tile. We are adept at measuring and placing a soap holder or shower caddy exactly where you want it and drilling through the tile. We use a bit of silicone caulking on the wall plugs before inserting into the wall and on the screw before inserting it into the wall plug to make a watertight seal. We also caulk around a soap dish, depending on the design, to further keep water out.