the pickup you are getting installed is critically important
the best ones available use Sennheiser elements and reject
off-axis sound best (to resist feedback)
assuming your accordion already has "the sound" you like
and want, then the only job an Amp has is to make it LOUDER
and
NOT
to act as a big fat tone control
so ANY amplifier that gives a generally flat response in it's specification
will work, but it is nice to have some Tone Control to "compensate" for
(low, mid, high individual tone control knobs)
the tonal deficiencies of a given venue, and a nice high quality Reverb/FX
section built in (not a delay, cheapo echo circuit) is also handy
it might also be handy if the amp has a "line out" for larger jobs
someday when there is a House PA system, so your amp processes your
sound and then acts as your Monitor on stage, but the House system
makes you loud
there are some more modern, modest priced but fairy powerful battery
powered amps available now as well.. enough for busking and small pubs
and ensemble work.. that means zero setup time and freedom of placement..
several of us use (battery) Roland Street amps of various types (several versions/sizes)
but many other brands are now available too
there are also small inexpensive wireless systems that work well if you and the Amp
are close to each other at all times, the built in batttery giving a couple hours of run tiime
and freedom from being wired is nice to have
here is one Prime day deal/model that i actually use in the Studio just for convenience
with the Roland's mostly, but should work with any Mic system with a volume control
more expensive wireless systems that use AA or 9 volt batteries and allow for movement
and distance from your Amp/reciever are more reliable in professional use, but if your Amp
stays near your chair the little one is fine
depnding on the mic and jack installation, i often leave one of these on my
accordions so that a wireless is in a more convenient and safe place, moving'
the jack from under the grill to up along the grill
(using black wire ties slipped under the grill work to hold it in place)
finally, there are some kinds of handy medium loud Battery operated
with built in Dolly/extending handles small PA systems sometimes called
"Tailgaters" that also have Bluetooth built in
(for playing along to tracks on your smartphone for instance)
that you might find more versatile for solo work
ION and PYLE are 2 brands in this genre, with SAMSON offering a
more professional/expensive version