I wouldn't use regular keepers, but the fish specific kritter keepers are great in my experience.
I kept my baby girl in a 1.75 gallon, the fish ones have exact measurements. She loooved it in there. I had a filter that was basic but had an airstone with some sponge baffling, some simple decor, and that was that. The filter is Whisper 3i which is 10$, Kritter Keeper 11$, and I got dollar store rocks that I 'boiled', and some fake plants given to me, plus a rock cave on sale for 1$. It held water fabulously, never cracked, didn't scratch.
Downside was the lid LOCKED on so tight that if I put the lid on then I couldn't get it off without multiple people, but never with water, so I sat the lid on top. Good news was it stayed secure and didn't slide off at all. Plus, there was a punch out hole for the filter/heater cords. I find the hole to be a tad too large, though.
Downside was there's no light. Upside is the lid has lots of slats so if you used a desk lamp or something it could easily light it up. Plus, the acrylic is surprisingly see through and clear, so even daylight and room lights lit it up nicely.
The last downside was it is not portable in any way, I find my other tanks to be more portable when water filled. If you moved it, water could easily slosh out through the slating, and the weight is pin pointed to 4 corners while the rest is raised, so if you ever wanted to take it with you, it'd be nearly impossible. It isn't a good idea to move it when filled up! It is highly portable when not filled with water, though.
I personally adored mine, and if I didn't want live plants, I would definitely keep my bettas permanently in the 3 gallon one. They're very nice! Again, the fish specific ones!