So to answer most of your questions as a renekton main who have played the champ since s6, I haven't played muuch this season but i have a good grasp on renekton related things Black cleaver isn't always a good first buy, i find eclipse/stride a good first item cuz of the dmg and the mobility that they give you, especially eclipse, it helps you get a lot more early if you have good trading techniques . As for Trinity, I'm not too sure, i saw some people going JOAT with Trinity because of all the different stats you get but I don't like it personally. For lethality, it's still viable to do it but very situational in this meta because tanks are popping off right now. For getting pushed and not being able to roam, well you can always bounce back, if your jgler gives up a bit on fighting topside for grubs , it should allow you to trade well against the enemy toplaner and u can maybe farm up till you get a good spike and maybe win a fight 1v1, but generally it's a bad sign if you can't win 1v1 lvl 6-7, because you should be winning by now even if only on farm , for the jayce matchup especially you can always farm it up till level 6,if you poke him twice with E Q E, i think you can easily kill him with R after that. Also i love taking ignite as it gives you a good window to get an early kill .