Stay behind your minions and try to get pushed in after you got level 2.
If you are pushed in, you will have an easy farming time, use Q or W if you are out of range.
Wait for jungler and then use smart E's you can make an offensive flash and E in front of them, this weill give you easy kills because the enemy has to decide really fast and leads to missplays really fast on lower elo, in higher elo you will force them to flash, I would do it if you can get at least on of them even when they flash.

-Use minigun only on single targets, it's really strong when you use fervor so i don't see reason why I should go with Rocket in a 1v1.
-Use Rocket against more than one target and when you want to harass in lane/siege towers with E+Rocket or want to get farm with increased range.
-When your passive procmores, go with Rocket Launcher on any target if you have at least one AS item + Berserker's.
-When you have no AS item yet don't switch on Rocket in fights, unless passive procs or want to finish somebody out of minigun range.
-Harass in lane like this: Get 3 Stacks on minigun passive that will not increase AS on Rocket but will decrease the time needed for the animation of the first shot on Rocket Launcher. If you hit Zap go with Q to poke out of his range, so he can't attack you.

after you have your Infinity Edge, Runaans and Stattics or a tower is fallen on bot side feel free to go mid and play around objectives, jinx is not a champion to solo/splipush with.
In teamfights stay back first and try to ger the passive prock, then only use Fishbones and you make heavy damage. Because of the increased range you can start focusing their backline more, but this always depents on the matchup and who is fed. Always try to get your E out because the chance is pretty high to get at least one of them in it and this can cost his life then.