Gloomspire Gitz are a ton of fun, have lots of options, great new sculpts and generally are a lot of fun to play against, which is important if you're mostly playing the same group.
Cities of Sigmar is an interesting setup as well, as this will make a good army to build into, based upon what you enjoy as you play. Like fantasy marines? Go Stormcast, like mortals? Build them up. Lot's of directions you can go and very fun thematically.
I'm a big fan of Daughters of Khaine as well, I think they are a good mixture of finesse and hammer.