I don't think that for lower level users (under 18) it's viable to go to other waterways.
For the time spent + money / exp gained lonestar just out-competes everything else. A $200 license with a 3200 net (for 20kg) beats out anything. The next easiest is mudwater with a 1200 minimum + license for an 1800 net, and that's with getting bass + trophies. The time spent on both waterways was about equal as well.
There has to be a change to the lower level waterways to make them a viable place for new people to go to, currently I've lost 3 of my friends who I tried to get into this game because they just bankrupt themselves trying out the new places.