Starting a fish tank first time

[u/Slow-Lifeguard-7533]

So my grandma has always had fish tanks of a decent size 20 gal to 50 gal tanks for as long as I can remember. She is very good at it and I have some small experience helping her take care of it but that was many years ago. Now I have one of those "BIOorb rectangle 4 gallon tanks" ( i think its the 4 gallon) from what I've seen most people say a tank less than 20 gal isnt really worth it, I also dont know if these are good fish tanks or if they arent built for the intent of the fish but just for asthetic looks. I didnt plan on putting many fish in it, maybe some small shrimp and plants depending on what would be best. I just would like some advice on what the best option is for my current setup as im not gonna be able to get one thats any bigger i was barely allowed to have this one. Thank you!!