We've made a selection of excellent starter reg's (short for regulator) if you are just new to scuba diving and don't want to spend too much.
"A scuba regulator is a device that allows a scuba diver to breathe air from a high-pressure tank while regulating the flow and reducing the pressure of the air to a level that is safe for the diver to breathe. It typically consists of a first stage, which attaches to the tank, and a second stage, which the diver puts in their mouth to breathe from. The first stage reduces the pressure of the air from the tank and delivers it to the second stage through a hose. The second stage has a valve that opens when the diver inhales and releases air when the diver exhales. It also includes a mouthpiece and a pressure gauge that indicates the remaining air pressure in the tank. Scuba regulators are a critical component of scuba diving equipment, allowing divers to breathe safely and comfortably while exploring the underwater world."