Welcome to the UU! You'll get good info here.
It's sounds like this is your first entry to be electrified. There are a lot of options so it's good to clarify what you are looking for in an amp. If you are looking for a clean guitar sound playing an acoustic instrument, then an acoustic amp. is what you want to look for. If you play electric instrument; electric amp. Loopers and pedals go between the instrument and the amp. Different amps have different effects so ensure you choose the ones you like.
I recently bought a Yamaha THR5A amp from recommendations here. It's super small, sounds very clean and weighs 5lbs. and sits on a shelf. I use it for gigs with a serious uke group. I can USB to my comp if needed. The speaker is small but is handling what I'm asking it to do. I'm amazed something this small can put out the clarity and volume it has. I'm sure it's the same with the other ones mentioned already.
I'm using it with a Chennel archtop baritone, K&K twin spot p/u with a volume control wheel and K&K preamp. Actually I sold it last night perhaps to look around to find something better. For my needs, this little Yamaha is perfect. The woman I sold it to, put it in her shopping bag with the rest of her gear and off she went. It's that portable.
The thread came at a good time; so far, I leaning on getting another 5A. Buying a Lehman lithium battery to go along with it really made it more efficient and portable. I used it over 5 hours and still had lots of battery left. Slides into the side pocket of a uke crazy case.
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