Is this a 210 liter tank (~55 US gal)?
I would first probably think about rehoming some of the gouramis. IMO, having three different T. trichopterus (not known for always playing nice) plus a pearl and a moonlight is too much...especially if the cosby/gold/3 spot combination takes a turn for the worse. Again, the pearl and moonlight are NOT variations of the "blue gourami" if IDed as such, which isn't always spot-on when it comes to common names. They are both recognized as distinct species.
A clown loach by itself is not ideal (they need more than just a "mate" too), and if it is currently in a smaller tank I would remedy that ASAP. That being said, if this is a 210L/55 gallon tank then it isn't exactly the best long term housing for clown loaches either since they can reach over a foot in length. If I remember correctly, they do seem to have the reputation for growing out to about 5-6" relatively quickly and then growing at a really slow pace after that, so you might be okay for a while. But then you also have to consider that trying to rehome a larger loach is much more difficult. So it is your choice what to do, but definitely do not plan on keeping any clown loaches in that current size tank (or the 210L/55g) for the entirety of their lifetimes.
As for what you could eventually stock, I say you should try to get a group of the typical "schooling/shoaling" fish in there...ie. barbs, danios, tetras, or rasboras. If you fix the gourami situation you would definitely have room for at least 8-12 of those type of fish, depending on the ultimate size of the species you choose.