Something to understand about fishing is that you can't really get past level 50ish without a LuShang's Rod. At this point you'll have trouble landing fish in the right size range for any rod you are using which will cause you to either lose your catch because it's too small or cause your rod to snap because it's too big.

I'm sure you know about the LuShang's quest in Sandy. There are some guides for fishing nothing but carp while leveling to 50 so that by the time you get there you will have a LuShang's Rod.

I can give you some advice, but I need to know more of what you want. Do you want super fast skill ups? Do you want high profit all the way? Do you want to work on your LuShang's while leveling up?

Either way I can say this which is pretty much the same regardless.

1-11
Use something like a Hume Rod and go to Knight Well in West Ronfaure. Use little worms. You will catch Moats and Crayfish. When you hit 7 switch to Insect Balls and go from 7-11. This will cause you to only target Moats.