Vi Tactics

i need someone experienced with Vi to tell me how can i be the most effective with Vi,just bought it had 3 matches with it and i couldnt be good with it up untill mid-game,even then i couldnt realy get a hold onto things and had to fall back from a fight with max hp most of the time because i knew that i wont be effective there,so my question overall,how can i improve with Vi?