As a long time gold ranked Garen player this is my skill order
Start with 1 Q for easy last hits and learn to use it a split second after an auto attack for more burst on a minion or champ. Also use it to sprint out of a bush to grab a minion and return to saftey if against a ranged opponent.
At level two if you are against a ranged opponent (teemo, kayle, vlad, elise are all common ranged tops) then get 1 W. It passively increases your defensive stats, you get more value out of your armor and mr runes and take less harrass
Then the next 3 levels are E. So by level 5 you can start trading for serious damage.
From level 1-4 you basically just want to manage your lane and farm without pushing at all, cheekyly Q them an run off if they get too close. From level 5 on you can start spinning for da winning but until you have at least 3 levels of E you are not a threat.