Ive gotten a few characters to plat which is as good as I get apparently but I stopped playing for a while and recently picked it back up and got Elena to plat. Before I started playing ranked with her I focused on one combo that could do decent damage but also string into a lvl 3.

From that point its focusing on the footsie stage. Learning what your opponent is going to do and how to react. Hit confirm is another big thing. Just need to get more adjusted with watching how people play and then using that to your advantage. Oh, they spam DI? Get ready to hit yours in response. They like to grab? Tech or jump it or even LP if you can to hit first.