There’s four core things you could need for the bathroom:

1. Bleach gel for the toilet bowl. Can also be used on other porcelain surfaces, but not for metal or natural stone (if you don’t want to ruin it).

2. A calc remover to remove calc deposits outside the toilet bowl. Can be substituted with either vinegar or citric acid. Can be used on metal, but do not let it stay on for long - 30 seconds is fine if you clean every 2w to 1mo. Even shorter times if you’re truly regular with your duties.

3. A degreaser for general cleaning (to remove soap residue and other nasty stuff). Can be substituted with dish soap, but is usually a bit more effective so less scrubbing needed.

4. If you get clogged sinks, those declogging solutions are okay. As most people have PVC piping you can just get the cheapest one. If you live in an antique house/apartment with lead piping, you should splurge on the enzyme-based variety, assuming you need it in the first place.