How does a returning player farm good characters now? (ie Fantastic four)

still learning which characters/teams to go for.

But now I decided that I want to make a Fantastic four team at least.

Is there no better way than getting 5-10 shards randomly in the shop, or some have nodes? No quicker way to get the 100s of shards to make a useable character of at least 5-6 stars?⭐️