Welcome to the MX5 club guys. Read the manaul at least twice. Try all metal mode to locate your targets then switch to decrimanate to check them out. If you are in a high trash area you can run in decrimanate with as little as possible notched out. Most of the post mention notching out the bottom 3 or 4 to knock out iron if you are searching for coins and jewlery. My most common settings are 8 on the sensitivity, 75 or higher on the volume, 2 or 8 tones, and 15 to 20 on the threshold. Nickles will fool you by coming in lower than 20 on the scale. I found had them come in at 14-18 often. Small gold and charms can come in low in the 6 to 10 range, usually repeatable but can jump around the deeper they are. The MX5 will go deep. I have found silver dimes at 8 ito 9 inches with a solid repeatable high 70s reading. For trash areas either the 5.3 coil or the 4x6 Shooter coil is the ticket to hitting the good targets. A good pin pointer comes in handy, and just put the detector in suspend mode while you dig your find.
Happy Hunting and Happy New Year.