I'm new(er than you) here and still trying things out. Trying to get the hang of things. Slowly but steadily.

I assume you've added #tags of interest, so you get a decent stream of posts
(just do a search for #WhateverYourInterestIs and then [+] add that search, one at a time).

I think you should be able to "follow" yourself on Pixelfed, and then you can re-share those posts on Friendica. Just make sure to tag those posts as well.
Untagged posts are basically just shouting into the void (those Following you will get them, though).

If you find a profile that posts stuff you're interested in, Follow them.
Some may Follow you back.

That's just some thoughts. It's past my bedtime here. Good luck, and good night!