If you don't have a support for peel, CS with your rockets, and try your best to stay behind minions (especially if there's an enemy Thresh waiting in the bush). To poke, use your W; if they're standing behind a minion, wait until you know the minion is about to die, and shoot it just as the last bits of damage are hitting it. Or, position yourself to hit them (and Zap is also great for checking bushes).
You can also poke with your rockets. If your enemy is standing near a minion that's about to die, you can just last hit that minion with your rocket, and the AOE will hit your opponent as well! You can also hit them with your rockets when they walk up to CS. Jinx's rockets are her best poke since it does AOE, and you can do some fairly decent damage to your opponents in the early game. Just make sure you don't use it too often, or else you'll run out of mana quickly.
Poking efficiently comes with practice, and there's a lot of "Risk VS Reward". But if you practice her correctly, Jinx is super strong! You can do it, I believe in you! ᕙ(⇀‸↼‶)ᕗ