Time to invest into FP units!

Emiya is good now with his 2 strengthened skills, Euryale and Robin are good too but more niche, so if you have limited materials I'd level EMIYA as he's the better general usage/wave clearer crit servant.
Hans actually pairs nicely with him, helps him with arts chains and the crit damage buff/stars he makes are things that help EMIYA do his thing.

Mozart pairs great with Chloe, he gives her arts buff and stars to let her really deal out damage.

Basically my recommendation would be level Hans, Mozart and EMIYA for easier farming/boss killing, Saint G is a good to raise too but Mash can tank well enough that if you've got her leveled like you do I'd focus on the others.

Always level Hans. He's about as important as Mashu.

Arash and Spartacus are great farmers which require low investment. For hard content, Georgios is an excellent tank and will buy you time for hard battles. Shakespeare is another good one, having a targetable 20% NP charge and a party wide buster-up. Euryale is great against enforcement knights and Gawain during Camelot.