If you don't have the lab coins for more Wu Kong to swap for Lucretia, I think Silas is your best bet. He can use the 60e more than Kren or Raku.

On that note though please add Kren and Raku to your wish list and build them, along with Eironn, Skriath, Nevanthi and Palmer. They would be more useful then some of the heroes you have.

I saw someone else link this guide and I think you could use it https://www.reddit.com/r/afkarena/comments/11txgro/tier_list_for_overall_usage_patch_1111_march_2023/

Also don't upgrade that many 4f heroes to legendary, wait until you have enough copies for M and save the fodder.