Just to throw a curve ball in here, a 30 gallon is often used to breed Apistos in and people often have 2 species in there but its not an exact science so you need a back up plan should the males become uncontrolable its often a good idea in mixed tanks like this to have a lot of things to break up line of sight. In the wild Apistos often live close to the edge of the water or in tiny creeks where there are a lot of over hanging roots, leaves and twigs and branches.
Also Apistos are hareem breeders so often need more than one female to a male.
A bit more info to think about as well, there was a member here a while ago who found reference to Apistos living in colonies of hundreds and sometimes even thousands in very small areas and was planning to replicate this in a tank, he even got in touch with the expert and legend that is Alf Sthalsberg (spelling) and he confirmed he had observed this behaviour in the wild and he often thought the way we kept Apistos in the hobby was odd, as in a pair of trio in a bit of a comm tank when you would be better off with more of the species in one tank to spread aggression around sufficiently that none of them became a threat to each other and they got on with it.
For me though if you are looking for a nice mix perhaps go for an Apisto species that has a really attractive female like the Panduro or Nijseni which have bright yellow bumble bee females and stunning males!! Then get 1 male and multiple females similar to the numbers Alf would recommend with as many as 8 though 3 or 4 females would work well in this size tank if you are not comfortable keeping cichlids at the moment.
Alex - your Dwarf Gourami are in a way similar to keeping an other Apisto in there as they are reasonably territorial perch like fish the advantage to having these to other Apistos though is they take their territory on the surface where they make their bubble nest rather than on the ground where the Apistos breed. Also if you have a pair at the moment I would consider an other female as they are hareem breeders and at one point or an other your male may need to much "attention" for one female to handle which can end badly.
Wills