Jealousy intensifies - uhum, great, great line-up right there, and great prospective picks for further grails.
As was pointed out, going by what class appears to be missing among your premier line-up, the obvious choice to level up would be a couple stickpeople - of those you listed, both Eli - congrats on getting her to NP5! - and Tepes would be natural picks: Tepes can taunt on the side too and you’ll get a lot of mileage out of all-girl teams with Eli’s sadism up, so do raise her and get her rank-up done ASAP. Try borrow an additional Eli some time too for additional memery.
Lower rarities would be equally good, too, however, provided they got NP-levels. Taiga in particular is a solid, reliable bow-breaking lass once her NP hits that much harder, original blue Irishman is also a popular pick among 3* to level due to his durability.
Other than that, further choices on who to raise can be made based on card-buffs: foxy lady will be fantastic for your arts-users, chief among them Salvatrix Mundi, Nito and, should you decide to raise them, Captain Purple and best Douji as well. If you got him, think about raising Leon too and finish his rank-up to unlock War Cry, great boost to your buster-quartet Gil, Ramses, Ina & Francis across several turns and doubles as a taunter. Speaking of taunts, Lips-lady and Georg would be nice to see fully maxed too, they can positively make single target-nuking bosses a breeze.
Either way, whichever way you go, you’ll have a blast with your crew, I have no doubt.