PROS

+ Easy champion for begginers to learn.
+ Decent range to harass in lane.
+ Good burst and one-shot potential
+ Has realiable CC to secure kills in ganks and help her and her team overall.
+ Really fun to play with.
+ Low spels cooldowns.
+ Low ban rate.
+ Can one-shot ADC's.

CONS

- Low mobility and no escape tools except Flash.
- Get outranged by most ranged mid laners which gives you a hard time in laning phase.
- Hard to recover if falls behind.
- Gets easily ganked.
- Easy to master but difficult to play in high elo.

Flash

It is essential for Annie because she has no escape tools and is necessary for her to engage and disengage. Also she can perform the Flash + R Summon: Tibbers combo.

Ignite

It is standard for Annie since it provides a lot of damage to finish off targets and increase her burst. Moreover a great counter for healing matchups like Vladimir bue to the grievous wounds it applies to the enemy.

Teleport

Is very good option for roaming in other lanes in cases that you can't beat your enemy laner and you want to pressure the whole map. A good roam is bot lane to one-shot the enemy ADC with your R Summon: Tibbers.

Dark Harvest
It is a great choice for Annie because she has good mid-late game scaling and this rune enchances that scaling. Electrocute is also a good option but it is mainly early game. Electrocute's late game is very weak, though it could be used for beginner Annie players for more burst damage and easier early game overall. In late it gets outshined by Dark Harvest but is a viable option more like focused on personal preference. More burst for one-shots and dominate early game? Or better late game scaling?

Cheap Shot is very good for Annie since she has reliable stun with her passive Pyromania and the extra true damage to burst enemies down. She can impare (stun) a lot of enemies at once with her kit and thus cheap shot will always be at use.

Eyeball Collection this section is up to personal preference overall. Though i prefer Eyeball Collection for the scaling in the late game. For insane one-shots.

Ravenous Hunter offers great sustain through the laning phase. Relentless Hunter is also an option for roaming but the healing is better and since you will be dealing massive amounts of damage the healing will also be massive.

Transcendence provides some nice ability haste but the best part is the CD reduction on your abilities per champion takedown.

Gathering Storm the whole items and runes are aiming to late game and this rune does too. It may seem minimal added AP but as the game takes longer the benefits are getting bigger.

When you want to Flash + stun someone, prefer Flash + W Incinerate rather than Flash + R Summon: Tibbers beacuse the Flash + W combo is faster and leaves the enemy almost 0 reaction time.

When having 3 stacks in your passive, you can Q Disintegrate someone and as the Q is flying towards him, you can cast E Molten Shield, (or any else ability), to get the 4th stack and thus your Q actually stuns the target but without letting them know earlier with your full stacked passive.