What Belongs in a Starter Kit

Kits vary enormously, and the gap between a complete one and a box with a tank in it is usually the water conditioner.

The non-negotiables

Tank, filter sized to it, heater where the room needs one, water conditioner, and a net. Without a conditioner you cannot safely use tap water at all.

The usually-missing pieces

A thermometer, a test kit and a syphon for water changes. None are exciting and all three get used weekly.

What you can add later

Lighting upgrades, décor and background. None of them affect whether the fish survive the first month.