Can anyone help me make my team up?

I would use the remaining time on the reduced AP cost to try and max out Herc if you have the mats. It’s great to have Merlin but you don’t necessarily have the Buster Crit servants to go with him just yet.

Mash and Cu can do a great job of tanking damage and helping to keep Herc alive while he does all your damage for you. He’s a great solo berserker and with those two protecting him you can have him dish out massive damage.

David pairs well with Mash for stall. Their triple arts deck assured they can fire off their NPs and David’s defense will be increased by 100%.

You have servants to generate Crit stars but I’d really be putting all the focus in Herc for your damage. Let Mash tank for him, she can provide him another invulnerability to keep him out there even longer. Leonidas is another easy to acquire servant that will once again extend Hercs life and allow him to keep doing what he does best. I’m sure others will come up with some better comps for ya, but that’s what I would be focusing on. Definitely the type of team I was running before I was filled out with rare tier servants. If you need some support help my ID is 825,960,988. I’d be happy to except a request if you think my team can be of help to ya. Just let me know and I’ll keep an eye out to except

Try to level all of them as best as you can cause they all have their usage. But if you are stuck on time, level up mordred, mashu and herc to max as fast as possible. Level up Cu chulain as well if you like. Those servants are the best servant to use for hard content you have right now and are your priority.
Your team can be Herc, Merlin, Friend Merlin, Mashu and Mordred back line. It's enough to sweep through story with ease.

Get the mystic code from the rare prism shop(if u want) and support(usually Hans)with ce the year of 2030 with invested bedi and Merlin’s np would be good,18 stars guaranteed for three turns unless u manage to fire off more np of Merlin plus two crit buffs from Merlin and Hans with multiplicative Attack and buster boost

561,490,085 If u are in need of ce 2030 Hans and farming archers