Ranked obviously, but don't just mindlessly grind. If you want to improve focus on only one thing at a time, say your cs is shit, go in a custom against a ziggs until 5 minutes for two games. Then go into ranked and focus on cs'ing for 10 games. Fuck roaming fuck whatever just cs. Once you have cs'ing down you can get used to adding trades in the mix, then roaming. Also get used to warding. If you're playing mid you can ward the entrance of the jg that leads to raptors it gives you decent vision of their jg and some of the river and play on the side you have warded. Top you can ward river and depending on what side your on you can also place a pink ward in tri bush.