I have been thinking about creating an imaginary world, too. In fact, I have been creating them in my mind. I have to find time to put them down in writing or at least dictate into the recording app of my phone.
Evolution of species.
A story is more intriguing if it has background of how various species evolved from a couple of common roots. It's more believable when you invent the history together with how they became known by what they are known. Then your story could prequel respectively into why they are what they are called.
Evolution of Language
It's not difficult to invent a language - if you have been exposed to a number of languages. You could have all these historical evolution of languages that is hidden beneath your world/universe that the audience does not know about. Every conversation - you drop a little hint. And you name their race and species based on the linguistic evolution you have concocted - which you could plan to reveal in bits and pieces as the story progresses.
I don't think we need to come up with whole vocabs for the languages. Just bits and pieces. Not trying to invent languages, but fragments of linguistic and cultural history in order to name your characters and their villages/cities and races.
Analytic languages (English, Indonesian) are easier to concoct than synthetic ones (Greek, Latin, Sanskrit) or idiomatic/ideographic languages. Synthetic languages require you to synthesize whole complex paradigms of grammar - which would be to complicated for a readers more interested in the story.
You start with inventing the primitive sounds - let's say rr, vv, hh, gg, mm. Threatening sounds, soothing ones.
For a very simple example,
Associating rr=exposition of power, gg=food, vv=ecstasy, mm=fear. And then the vowels would indicate intensity u e a i.
So ruve gami would be someone with some power exhibiting it in mild ecstasy over those who have strong need of food and extreme fear of losing their source of food.
You should try to be consistent. For a particular tribe/race - is it "house my" or "my house" to denote possessive. But not overly consistent.
Then the race/species gets splintered evolutionarily. Or a less developed tribe encounters the first tribe and adopts their grunts - but they could not pronounce r because of their biological limitations and all the r sounds become y sounds. And they had mixed up the vowel intensity. Instead of four intensities, they only have three.
So the new tribe says yaba hhene rather ruve gami. And they have a different culture - more aggressive. So ruve gami=village mayor becomes yaba hhene=fearless king.
You could name species after the places they are associated with, using the various grunting languages you have developed - for example, the house on stinky river = giba ngonle. n being negation of food = stinky.
And then their names get evolved thro diversity until the present day of your story. And when you form the conversations (in English of course), their manner of speech (which you translate in English) and the body language you describe of each tribe or species hint very strongly of their past linguistic and cultural and adversarial evolution.
It's like the shampoo advertisement telling you to give body to your hair - give body to your story - when the epic of story is woven with the names of the races and cities, geography and languages, with its linguistic and historical evolution. And why they are fighting or are in uneasy alliances.
Because of the simplified analytic language you concoct, your readers will be able to learn them quickly. And when a race or city is called Ngandi-Kopsela - your audience would get a hint that species had been named pejoratively by another race. And they would more likely want to find out why that race has a pejorative name and who amongst the subtribes gave them that name and why.
Because your universe is so rich of untold history (all hidden in your foundations scrap book) thro its names and simplified languages - it could make readers crawl the episodes to find out, to decipher or to wait for the next installment.