Back when I had potato internet which made it a nightmare to maintain a good ratio I did try using a seedbox, and only for a single month at a time. It's been ages since I had to do it, but all I did was add anything new that looked like it would become popular. (Think popular performers in the busiest categories. That sort of thing.) I'd jump onto anything that:
-
Was uploaded very recently, preferably in the last few hours, and
-
Had only 1 or perhaps 2 seeders with lots of leechers, and
-
the bigger the download the better, (Simply means there's more upload traffic to be had)
You ignore the whole concept of downloading what you want for yourself, and concentrate on what others are hungry for, and the high speeds you get make you a very attractive peer to connect to.. As I say it's been a while but I seem to remember being able to farm in excess of TB of upload credit in a single month that way with very little effort and I'm sure I could get even higher rewards if I really tried, all for the paltry sum of about £10 to £15 for the seedbox.
As @ianfontinell-0 says, you need to look at how big your deficit is first. Then you know what it will take to fix it. If you give us some numbers I'm sure it'll be an easy task.