On one I "fought" with my broker/property manager on where I wanted to (and did) complete major outside renovations and a parking lot refinish where he suggested I focus on units and make readies. 

Refinished the hardwood floors upstairs and downstairs, installed groutable vinyl tile in first floor kitchen and shared hallway, new cabinets, faucet, sink, and stove in first floor kitchen, repainted entire interior, reinforced upstairs porch, replaced some support joists for upstairs porch, painted both porch floors, built new upstairs porch railing, installed new vanity, medicine cabinet, and toilet in first floor bathroom.

New paint for sure, maybe new flooring or refinish hardwood floors. 

We’re planning to add an additional bathroom to the main unit to improve value, refinish some surfaces in the downstairs unit, and landscape our backyard.

Refinishing cabinets & add backsplashpaintreplace carpet with vinyl or lam plank

I've installed and refinished a lot of oak flooring.

- Ceramic tiled shower enclosure or refinish the fiberlass already in there?

It will depend on the market in your area and the condition of the original floors, but generally I would say YES - its generally more economical to sand down and refinish hardwood then it is to replace it. 

I refinished the exterior, renovated the pool and updated the landscaping.

Refinished whole house hardwood floors.