Play games
Choose the game that interests you and play itfor free.
Complete the quests
Every game has some quests for which you will receive Soul Gems.
Receive rewards
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
Back-to-back events are a pain to deal with, unless you actually like grinding.
https://fate-go.us/news/?category=NEWS&article=%2Fiframe%2F2020%2F0801_servant_festival%2F
This time it's a ladder event, and grinding is inherent. But everything is made more complicated than usual due to a *spoiler* mechanic screwing you in the first few days. Then you'll realize it's pointless and back to grinding more; the game will sort itself out if you're diligent enough.
Welfare Jeanne Alter Berserker is exceptionally good to use which is as usual for welfares these days. Not compatible with Skadi System mind you, but don't let that get in your way of getting her to NP5 80 1/6/6 at least. Explosive Berserkers are always in need when you just want to get it done real fast.