Honestly, this question is one that I cannot seem to find the answer to.
I have been using private trackers for the past 5 years, building a big ratio in every one of them.
Recently, I started using seedboxes in an attempt to finally start upping my game and get into the bigger trackers.
The thing is, the ratio I have accumulated on the other trackers seems to be mostly useless, as most of them are 0DAY/General so there isn't any recruitment thread.
The other trackers I am on are extremely obscure and the forums are dead.
So, my question is, how do you do it? How do you start getting into more trackers? Thanks!

Seedbox is one option as you mentioned.

If you have a fine internet connection just care to seed a lot of files (1TB+) and it will do the job. Don't forget to cross seed your content ofc.
After Getting into higher tier you will proably be able to upload content. This is a great way to build your ratio.
You will be surprised, but actually rather than trading or waiting for lucky givaway your best way to climb is actually dedication as I mentioned and later recruitment threads in various trackers. Even FL has one. Some has applications open sometimes which are not being promoted publicly.
Joining discussion and getting to know people won't do any bad, especially in the highest tier trackers you will reach..

Good luck.