Good advice so far, what I would add is know your 'magic'.
i.e. how does your jumper's/planeswalker/etc power work? Under what conditions can or can't be used? Establish it early and don't deviate from it, either to nerf or buff without a very good long build-up (avoid the nerf in general)
Cause if you don't, and unless your mc is 'built' in a way that they wouldn't run when things get rough, readers will rightly complain of rail-roading if they don't use their powers to run from, say, Cthulhu when they're a lvl one mook.
And know your 'magic' in a general sense as well. What powers will the mc acquire, what are their limits by themselves,
if (some) can stack together what can they achieve etc. Work? Yes. Will make for a more authentic tale? Also yes.
Another trick, powerwise is... you're the writer. If a power would be too complicated for 'x' point in the story... don't go in that universe just yet. You're the writer. You decide the order. The portal making power and its destination might be 'random', on paper, but that doesn't have to be the case irl.
And one last bit, emulate
good gamer fics/self-pub books. Meaning mention the powers, of course, but don't constantly keep filling page after page with descriptions of them etc. Rather describe/show their effects when used.
In other words, a jumper tale is no different from a thriller than it is from a romance is different from fantasy etc, etc. At the end of the day it's all about plot and character & the interactions between them. Everything else is wrapping, with each genre having its preferred conventions and tropes...
Oh, and yes, relating to the character bloat and thin plot, as f0ri5 rightly mentioned... think of each 'world' as an isolated island, for the most part, with its own tales and cast of characters. Few of whom will have relevance, be mentioned again on the wider story beyond how they helped the hero grow/evolve. Meaning, don't rush through each world, have a tale and threads and a cast of characters as big as needed and only just.
Good, examples of that, even though its not a 'jumper' tale, so to speak, is Onepiece and QQ's very own AStoryForOne's '
A nascent Kaleidoscope' which
is an
excellent planeswalker tale.
By the way, if all that sounds like its too much? Start writing and don't worry overmuch about it. Tackle it one bit at a time, and as long as you keep reading and writing? You'll improve.
