Here’s the tank It’s not the recommended size for a betta but if you keep up with maintenance and enrichment your fish will be fine.
I have a low-tech walstad-method tank, the only "tech" I use for the tank is a light for growing the plants. No ferts or chemicals besides using Seachem Stability to help the tank cycle early on, that stuff was super effective.
I bought this Penn Plax 2.7g tank for about $35, it comes with a filter but I only used the filter the first day to help clear up the water: https://www.amazon.com/Penn-Plax-Aquarium-Thermometer-Desktop/dp/B0069RPRHO/
If you want it no-tech I'd recommend having it near a window to help the plants grow, otherwise you'll want to buy a desk lamp with a CFL bulb to pointed over the tank so it can get light, I leave my light on for 10-12 hours a day at the moment. This is the light I ended up getting, but after a month and a half I'm not sure how much I like it compared to getting a desk arm lamp instead: https://www.amazon.com/gp/product/B00LMH10HC/
I don't have shrimp in mine yet because it's too early, but my understanding is that they like a lot of surface area, like hardscape and mosses and stuff, bushy plants they can hang around in, and maybe some floating plants for the clever shrimps who will hang out up there and munch on them. If you just need some plant ideas to start, here's what I have in mine: hydrocotyle 'Japan', rotala h'ra, monte carlo, stauroyne repens, duckweed and water lettuce.
Check out r/AquaSwap for plants to purchase, you can find recommendations or inspiration and more in r/shrimptank
Its the Tetra cube 1.5g.
I'm thinking about replacing it at some point with this because it's got some scratches on the front.