guide
A first week in League of Legends that teaches you something
Choose one role, make farming a separate exercise, and review a single bad decision after each match. Small targets make the Rift easier to read.

League of Legends gives a new player too many things to notice at once. There are unfamiliar champions, a shop full of items, teammates asking for help, and a minimap that seems to contain the explanation for every death. Trying to learn all of it in each match produces a lot of activity and very little clarity.
Give your first week a narrower purpose. Learn how one role earns resources and how one champion uses its abilities. Once those actions feel familiar, it becomes easier to notice why a lane position is safe or risky.
Keep your champion choice steady
Pick a champion whose abilities you can explain in ordinary words. Read the passive as carefully as the flashy ultimate. Riot's champion pages are useful here: Garen's page, for example, describes how his health regeneration depends on avoiding recent damage. That information affects when stepping back is sensible, not just how you fight.
Spend a short practice session finding the range and delay of your basic abilities. Use them separately, then in a simple sequence. If the champion uses mana or another resource, watch its cost. The goal is to stop reading buttons during an exchange so that you can look at the opponent instead.
Choose one backup champion for situations where your first choice is unavailable. Constantly swapping makes every match an introduction and hides which mistakes come from the champion and which come from your decisions.
Practice getting paid
Gold and experience make champions stronger. For a lane champion, last-hitting minions is a useful practice exercise: wait until your attack will finish the minion rather than attacking each one without a plan. Start without an opponent, then repeat in an appropriate beginner match.
Notice why you miss. Did you attack too early, walk out of range, or use an ability that changed the whole wave's health? Choose one cause to work on. A modest improvement repeated across several waves matters more than one impressive duel followed by a long walk back from the fountain.