Something around a 220L should be good. Still though, if those angels end up pairing up, I don't think they will be able to share the tank with the gouramis. I probably wouldn't keep a betta with a breeding pair of angels either.
Do you have a test kit? You want your readings to consistently be 0 ammonia, 0 nitrite, and 20ppm or less nitrate.
Gold gouramis and mollies can grow to a nice thick 5", and angels around 5" long and 8" tall, so you can see how a tank this size just can't accomodate them. If you keep fish for too long in an environment significantly too small for them, they can become stunted (internal damage), or even more likely, poisoned by a build up of toxins in the water.
is in the business of selling fish, and many don't seem to want to turn sales away by informing the customer they are overstocking their tank or purchasing fish too large for their tank. As a general practice going forward, I recommend you research any fish you are interested in before purchasing, and double check here on the forum with other hobbyists for their opinions on minimum tank size for a certain species and just how much stock will work in your tank.