You can still create a full tank! If I were you, I'd re-home all 3 mollies and instead come up with a new stocking plan. There's lots of nano fish available out there, and whereas they are harder to come by, they are just as exciting.
Here's a link with a bunch of fish that would work great in your tank:
I'd go with a small shoal of one of the types of cories on there (maybe 4 or 5) and then a school of one of the types of rasboras (maybe 5 or 6).
Or if you wanted, you could do a betta and then add a school of any of those listed on the page (5 or 6 in a school), or even neon tetras, which are super common and much easier to come by than some of those species.