If you’re searching out freshies, the absolute minimum you and everyone else in your party should be taking with you is the following holy trinity:
They come in many varieties but you should be after a digital, multi-antennae beeper in case of multiple burials. You should carry it strapped to your chest underneath your jacket but on top of your other layers so that you can get to it ASAP. They allow you to be found should you be buried, and likewise help you find your buddies if they’re the unlucky one.
You should be absolutely comfortable using it before venturing out with it, so why not get a friend to bury theirs and then take turns in finding it over a large area like a park? (Be wary, electricity and also metal object like cars can interfere with radio signals so find a deserted place.)
Essentially a long and sturdy tent pole used for poking around in the snow once your transceiver has located the nearest place to a signal on the surface of the snow. This should be as strong and long as you can afford (also avoid the ones that can be stored inside a shovel handle; they’re weaker and take longer to get to). Again, make sure you know how to properly extend it; each brand has a different quick-draw method.
Should be metal with space to put your boot on top to dig down with and ideally should have a ‘D’ grip in case you decided to wear your mittens on the day you have to use it, then it’s less likely to slip out your grip.
You should also have a lightweight backpack to carry all this in, keep all your gear inside the main compartment, there’s always a chance anything mounted on the outside could get knocked off in a particularly spectacular tomahawk, and keep this space as empty of other stuff as possible; you don’t want to be digging through camera gear and sandwiches to find your probe. ABS bags, which you can inflate if you do get caught in a slide to assist in bringing you to the surface, are expensive, but recommended.
The cost of this stuff can mount up, but you really should not be considering going off-piste without it; better to have spent the money and never need to use it than to need it and not have it.