Beginner Guide #1 - Rerolling Guide

What is rerolling, and why reroll?

Rerolling is a term often used when playing mobile games, which is the action of creating accounts multiple times to get certain cards on an account. Usually, mobile games will provide new players with certain amount of resources to be spent on the gacha, in which the player can get characters or cards. In Shadowverse itself, new players will get around 7 or more card packs in the beginning. The card rarities are divided by bronze, silver, gold, and legendary as the highest tier. By rerolling, people can start off with some legendaries they want which will save some time and effort to build the deck later on. 

So, how do I reroll?

For iOS user, sorry no easy way. You need to delete the app and redownload the app again. If your iOS is jailbroken, you can try this method:
Disclaimer follow at your own risk

• Navigate to your app folder through ifile, should be in containers>data>application or alternatively connect to your pc and do it through iFunbox
• Once your inside the app go to library>preferences and either backup or delete com.cygames.Shadowverse.plist if your on the US version or co.jp.cygames.Shadowverse.plist if your on the JP version. This file contains your ID information
• If you want to transfer between the two apps then rename the plist file to the other one.
• Reroll as normal.

The original method was posted in reddit:

For Android user, it's a lot easier. Just clear data and cache and you're done.

When should I stop rerolling?

Obviously, when you get the legendaries you aim for. However, I recommend to aim for 4 or more legendaries. If you're starting with 10 packs or more, it might take hours or even days, but it's not impossible. The legendaries drop rate is not as bad as you thought. 

Which Legendary should I aim for?

Maybe in the future I will write more in-depth guide for this, but for now I write a simple guide for each legendary.
EDIT: I decided to make a separate post. Please check here: Beginner Guide #2 - Legendaries Guide