Leona guide
Laning : In lane you want to look to hook always. Sitting in the bush helps with this. If they look to engage on your adc you must wait they blow all their cooldowns, similar to master yi. If you can get either of the opposing botlane below 80% hp hook for the dive. Thats all you need to know honestly.
Mid to lategame: Always look for that sweet engage whenever possible. If you ever engage and get collapsed on by enemy team and some of your team are the other side of the map or in base it's their fault so make sure to spam ping them.
Sometimes your team is in bad situation like your 2 inhibs down and enemy have baron so you may just play defensive, WRONG! Flash hook R into enemy team, if you stun enough you will win. REMEMBER ALWAYS HOOK!
Now onto build. Rush
everygame. Your full build should look something like this


That is all you need to know to reach challenger good luck friends!