Co2 i got a ?

i got a tank but dont know what kind of regulator to buy...probably just buy anykind.. but curious on how much to use where to put the tank basic stuff never used co2 before i hear it does great things....any info would be great..im about 2 weeks into flowering. heres a pic one one left fucked cause i left in someone else care the other looks good....

High Tech Garden Supply

there you go man

thanx bro ijust seen so many diff kinds dont know which to get