I prefer to take Q first because it gives better leashes and more presence and poke in lane early but you can also start w if you want to scout the enemy jungle. R > Q > E > W
Try to poke as much as you can with autos, q's and passives to make the most of your stupid op range that is highest in the game by far. Other than that just farm and get kills when you can.
You now have Ie and maybe phantom you can now q to waveclear. This is a big powerspike and you want to group when this happens to push toweres. Cait is really good at seiging because of her range so just push lots.
Just stay at the back and attack anything you can e away if someone gets too close but try not to waste it. Just keep pushing stuff and look for good fights. I'll send a picture in tgs chat that shows you a cool baron trick
focus whoever is closest/ poses the most threat. This does not mean focus tanks, if you see a carry out of position rek them with your range but yeah dont forget about the tanks you will shred them quickly.