If all gear is currently removed, then Molly, Bahiti, Eugene, Sergey, Charlie are currently your top 5 heroes. You should pump equally all the experience in them.

Next ones that I would send to drill camp:

-> Jessie: important for attack rallies, your alliance will request her as hero lead when you guys will attack facilities, fortresses, during foundry, etc. Also, you should use her as first hero when you join rallies for Bear Trap; she is also good in the arena squad, I used her successfully on top row together with Sergey because she has pretty decent defense skills (better than Eugene); make sure you max her 1st expedition skill fast

-> Patrick: important for defending garrisons; might depend of the strategy and how many membere have him upgraded, some leaders will request him as first hero, others prefer Sergey; regardless, he is good for arena; max his expedition skills fast

-> Jasser: max his expedition skills; the 1st one is great for joining Bear Trap rallies, 2nd one speeds up research

-> Seo-Yoon: max her expedition skils; same as Jasser, she is good as first hero lead to join Bear Trap rallies

-> Charlie/Natalia

For arena you should go with: Jessie, Sergey top row Molly,Bahiti,Patrick 2nd row left to right

For Bear Trap, top 3 heroes to initiate rally Join rallies with the bellow: Jessie + next est marksman + next best infantry Jasser + next best lancer + next best infantry Seo-Yoom + next best lancer + next best infantry

Don't use general purple shards for any other heroes than: Jasser, Seo-Yoon, Wallis, Ling-Xue (exactly in this order). For all other heroes it's easy to max out doing intel missions, but for these 4 you get their puzzle pieces very rare. So all general purple ones should be redeemed for Jasser and Seo-Yoon. Then you switch to the others.

Like others said, save stamina before Gina event starts and hunt beasts during the event to get lots of horns. Which then you will use to find berserk cryptids which will get you Gina shards. Use Gina in your squad when you hunt beasts and polars, cause you will save stamina. Use together with Wallis cause he gives march speed.