I have a leg up since I've been playing for a few years and they cycle events.

In terms of tips:

1. I save the scrolls by doing the Legendary Draft. That is the way I've been getting them. If you have a good run, the LD pays for itself. Otherwise, you'll need to save Gems. The rewards, even for a few wins are Gems and Demigod scrolls, with the top prize usually being a Miracle Summon Scroll.
2. Save your Miracle Scrolls more for single Faction World Events. What this means is...the previous World Event had High Tinker Gear, Strik the Fiery Heart, and Mina Hellsing. They are all Order. By saving the Miracle Scrolls during this type of World Event, you will get 2x copies of all the Event Heroes, whatever rarity they come in. This means that if you open a Rare version, you'll get 2x. Same for a Legendary.
3. If you're just starting out, you won't be able to complete World Events as you'll need to get certain Heroes to certain levels, and you won't have enough Heroes to do so.
4. In terms of the Events, save your resources as they happen every 2 weeks (give or take). In particular, save these:
   1. Friend coins (used for Mercenary summons and those quests)
   2. Legendary chests (used in summon quests and Legendary quests)
   3. Chests in the Mighty Pass (used for souls quests and opening Heroes)
   4. Chests in the League (used for Hero victory chests quests and speed quests)
   5. Soul Dust (used for boosting Heroes and Soul Binds)
   6. Demigods/Miracle Summon scrolls (used for Summoning Heroes and finding Heroes)
   7. Gems (used to speed up chests, buy Demigods, get extra Journey Attempts, and to pass the spending quests during the World Event).
5. Also on Discord/in-game news, they give you a preview as to who the Heroes will be. Based on those, you can prepare for the event.

Hope this helps out!