I know this seems awesome !!! Well it is . In order to create your own dream world you have to desire a barren place. once you have achieved this , you have to think of what you would like to have in your own little world . close your eyes and think deeply when you have finished, open your eyes and your world should be there (keep in mind this is all while lucid). When you have completed your dream world, you can bring any person, place , or thing you want into your world . My purpose of my dream world is to relax and be at peace with myself. When I wake up from my dream world I feel so much peace and it helps me have a better day. It is also a great stress reliever. Also Keep in mind it is a great place to have fun and goof off and do whatever you want to do in a lucid dream. 
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ive tried this before, but its not actually that simple.
to achieve complete lucidity, and i do mean absolute, complete lucidity, almost no difference from WL, every single detail must be there.
every twist, every corner, every wall of your city must be there, and your city only ever comes to life when it takes on a personality of its own.
this is just like creating DC’s, its almost exactly the same thing, once you manage to create a DC, thier personality and attitudes only come out after years of being born (created).
when i say before your city takes on its own personality, i mean the people there, the whole mood of the people, the location, everything cannot simply be in one split second, for the city to truly take shape and detail, it takes almost too long.
im not saying you didnt create your own city, but what im saying, is that your city wont take on a definate shape unless you continuously remember it the same way, otherwise the city would be everchanging, but to make your city complete, you need practice, and alot of time imagining where things in your city are going to be.
to an expierienced LD’er, the initial creation process is simple, but this is only the first step, wich is what you’ve already covered.
this wouldnt take long at all, about maybe an hours worth of thinking over the entire city while doing whatever you want, and maybe draw parts of it, idk this is where creativity plays a key role, you have to imagine most of the city before going there so the placing of the cities isnt as random.
after this, all you have to do is go there in a lucid dream, which is a bit more complicated than it sounds for non-expierienced dreamers. (dont know how many ld’s you’ve had)
after this, its nothing more than a figment of your imagination, no feeling to it, no real attitude a city should have. (as in feeling you get from the enviornment)
what you need to do then is build on to your city.
create it in more detail, imagine what kind of people would live here, wich DC’s live where, wich house is yours, etc.
after a while, like ive said before, your city will gain more of a definate shape, the only issue with this part, is it can take up to 2-5 years for it to become almost real.