Ability to change shape whether or not exist- That way I can turn into Various Pokemon and stuff
Ability to travel between in universe, reality or alternate dimension whether or not exist and this would include travelling inside of dreams as well- Then I would be able to travel between the Pokemon World and others.
And probably make so that whatever I turn into on the shapeshifting I gain the power of whoever I turned into so if I turned Yveltal I would be able to use Yveltal's power in that form, and if I wanted to use Dialga's power I would have to turn into Dialga. As far as turning into a dragon goes, my power for that would likely be to the dragon I seem to end up in dreams that have which I would be able to control darkness, create illusions, change shape, breath fire and poison. Although Darkness is its strongest element since it is primarily a dark element dragon and that dragon is also capable of seeing past and future related events at random.
I also been both Yveltal and Dialga before in dreams as well and know how much power both of them have.
Pretty much would have everything I would want and wouldn't need anything else. Although if I do travel between worlds that don't exist I wonder if that would cause them to exist.