Are you wanting a Pressure "cooker" for cooking food quicker or a Pressure "Canner" for pasteurizing (canning) food jars for long-term pantry storage? They are NOT the same thing.
A Pressure Canner with a dial gauge is for the sophisticated canner but it does require that you get the dial gauge checked for accuracy BEFORE you use it the first time and at the beginning of each canning season. Most of us no longer live in farming communities or near local Extensions that offer the testing so a "rocker gauge" pressure canner is more popular. You can also purchase conversions from a dial to rocker gauge for some brands, like Presto.
An inexpensive (under $70) rocker gauge pressure canner is the Presto 16-qt and can be found in most Wal-Marts, Ace Hardware, or similar stores that sell canning supplies. The expensive canners are the All-American and these get passed down in a family for generations.
Pressure Canners are used ONLY for processing low-acid foods (meat, vegetables). For high-acid foods (jams, jellies, pickled items) you use a Boiling Water Canner, which is nothing more than a big stock pot with a rack to boil jars in.
Rocker gauges have three (3) weight settings (5#, 10#, 15#). The 10# is the standard for modern canning and the 15# for higher altitudes.