I was just wondering, say you became lucid in a dream that starts out in your house or something like that and you wanted to have a big epic fantasy adventure or star wars type thing happen, how would you go about initiating something like that? Would you do something like say “when i go outside i’ll be in a fantasy world” or “when i go outside i’ll be in space”? I’ve heard that spinning not only stabilizes lucid dreams, but can also transport you to other dream environments. Might that be a good idea and can anybody think of anything else?
Personally I don’t like spinning. Both your ideas would work as would teleporting (I’ve done it by just shutting my eyes for a second and willing myself to be teleported), also jumping into a TV, picture or book would work. 
Or you could arrange for a dream character to pick you up in their spaceship etc.
Sometimes the best thing to do is try multiple things and see what works best for you. Personally, when I want something I just will it to happen, or to just “be”.
If you have trouble manifesting things on the spot, you could believe that are in an other location. A teleporter in the lounge, a space ship in the garage etc.
There is no “this will make this happen” when it come to dreams. I believe a lot of methods are really just placebo, because in this case it really is all in the mind. The only time I have ever spun in an ld it caused me to wake up, but this was before reading here that it can stabilise them.
So I would honestly say think about what might work for you based on experience, then just believe that you’re correct.
I read a lot of “portal fantasy” style SF – stories where characters start in the ordinary world and then travel to a fantastical world somehow – so that’s the first thing I think of. The wardrobe door that leads to Narnia, the TARDIS landing in your backyard and whisking you off to adventure, the magic key that causes any door to take you anywhere you want to go, that one bedknob that will turn your bed into a vehicle to take you to fantasy land…
An actual dream I had a few years ago–non lucid, sadly, but full of great portal fantasy elements–transformed my parents’ back yard into a perilous otherworld that (in the dream) everyone knew you shouldn’t explore because if you stay there too long you go crazy and die, but I knew I had to go because something I needed was lost in there. Talk about pure storybook adventure!
A more recurring dream element is the walk-in attic in my parents’ house (my childhood home). In waking life, growing up, I was fascinated by being able to walk into it in my bedroom, make my way through a cramped crawlspace, and end up in my brother’s bedroom. It felt like magic. So in my dreams it really did turn into a magical gateway to other worlds, or sometimes just a magic cave that only I could enter.
I hope some of these ideas are useful to you!