I know some may disagree, but IMHO bettas need 5 gal minimum, whereas the spec is about 2 gal isn't it? When my betta got his tank upgraded from 4 gallons to 7.4 gallons (15L to 28L), he became so much more active and definitely seems far happier.
If I were you, I'd get a standard 5-10 gallon from your local pet store or supermarket if they sell them. Get some gravel, silk plants, a small filter, a heater and you'll good to go once the tank has cycled. A light would be beneficial but not absolutely essential. If you didn't want live plants, even a desk lamp might be OK if the tank didn't come with a light fitting.
The lowest price I've seen for a spec is £30/$47. You'd probably be able to get a full 5-10 gallon kit inc decor for that price or less. Try going to one of those '$1-per-gallon' sales at petsmart/petco if you're in the US.
I would say the spec is only good for shrimp. Someone on here has one all planted out and it looks pretty good.