A guy who wants to improve

Hi, Me and my friends are a bit stucked at improveing. We have a group, called The Rusty Cage. Usualy we play in duo or trio at a time but sometimes we are able to play in full team. We are bronze-silver divs, so we have problems. I am bad at aiming and I usualy buy way too many potions. Our top can't play deff good, but I can. Should I teach him in custom? Our supp is can't play from behind. The others have minor or too many problem (they started playing a month or two aggo or just better than me and I do not see the problem). Also the knowledge of the runes-items is also bad for the others (I have to build myself, the supp and the top at the same time sometimes). We don't want to go e-sport but we want to improve a bit. Any idea? And yeah... the top plays a lot of mid as I gone from mid-top to adc-mid but it's complicated. As I see these are common problemes at low elo, so any tip could be useful to others too. Edit: as I read all the comments I think its better to share our team comp: Top-mid: plays a lot novadays but he left for 2 years and plays again for 2 month by now, aatrox main, bronze Jg1: zac one trick, plays nearly no games novadays, silver Jg2: very new to the game is have a little brother who is top and even more newer to the game, kindred and garen mains, both bronze (or iron, still in first placement) Mid-supp: our best player, annie-leona main, silver Supp-jg: do not know any basics only the champs (and not all of them) pyke main, bronze Me: adc-mid, recently changed from mid-top, miss a lot of skillshot, was diana main now wants to be jhin main, bronze