I think I can help you from the "non-seedbox" side of things.
The secret is to seed a lot of torrents. Generally, I have anywhere from 150-200 (177 currently) BakaBT torrents set to "Forced Start" ("seed forever"). Out of those, 15-35 will actually be active at any given time. I have no trouble at all fully using all of whatever % of my upload pipe I care to allow, generally 80% of max.
I've had no trouble maintaining a good ratio (~2.4; 4.9 TB up:2.0 TB down), even though my connection, like most people's, is quite asymmetric and I seed to the exact same swarms as anyone else. I don't pick torrents for "seedability", just for interest. So take it from me: build up a small collection (20-50 or so) of seeding torrents, and you'll start to see those numbers go up pretty well, without having to really worry about it. Remember, by the way, that it's not individual swarm ratio that counts, but rather the total across all of your torrents.