Many ARES/RACES Operators put together a "Go" Bag or Box. This contains items and equipment that allows you to operate from anywhere in the area on a moment's notice by just grabbing the bag and getting to your assignment as quickly as possible. The following are just a suggestion to get started. Your "mileage" will vary depending on your budget, how much you can carry, and how long you expect to operate for.
Most Go Bags should sustain you for 24 hours. After that, you probably will either have relief from other radio operators, or we are able to get in other supplies and equipment. You should not be completely depending on the served agency for supplies, although you may get some.
Basic 24-hour Go Bag:
Dual-band (2m/70cm) handheld radio.
Fully charged battery on the radio, at least one charged backup.
Speaker microphone and/or headphones.
Printed frequency list.
Amateur Radio license.
Notepad and pens/pencils.
Log sheets.
Small flashlight.
Cellphone and charging station.
48/72-hour Go Bag:
Dual-band (2m/70cm) mobile radio (25-50 watts).
20Ah LifePO4 battery with solar charger and panels.
Anderson PowerPole adapters for batteries, car, etc.
Portable antenna (roll-up, J-Pole, telescoping whip, etc.)
Antenna supports.
Portable battery for charging cellphones.
USB cords.
Extension cords.
Power strip.
Spare fuses.
Basic tool kit.
Personal Items:
Water for initial deployment.
Non-perishable snacks.
Prescription medications.
Rain gear.
Jacket or extra clothing.
Hat.
Sunscreen.
Insect repellant.
Work gloves.
Safety vest (if required by local group).
Hand sanitizer.
Small first-aid kit.
Optional but Useful:
APRS-capable radio or tracker.
Meshcore node.
Portable mast or painter's pole.
Mag-mount mobile antenna.
SWR meter or nanoVNA.
Spare coax.
Anderson PowerPole connectors and tools.
DMM.
Small folding chair.
Clipboard.
Laptop.
USB flash drive.
Portable hotspot.
Headlamp for hands-free light.
Documentation:
ICS-205.
ICS-213.
Local MCARS Frequency Plan.
Repeaterbook.com on phone.
County maps.
Contact list.
Radio manuals.
Emergency contact information.
Even if you have the budget for all of this equipment, it is advisable not to purchase everything at once. Work you way into it based on your actual needs. It is better to be agile and light rather than bogged down and struggling with excessive equipment that you never use or can't carry.