>>9515500For history stuff it can be tricky since fantasy-themed Novelmore has displaced the traditional medieval themes.
Any Roman or Egyptian set is great. They are recent and whatever you can find of those will be a great purchase.
A couple years ago I bought the 6005 hay cart set containing Hawk Knights and I liked them. They are one of the last knight factions released so you may still be able to find some sets, and I think their colorful red emblem makes them work great as a blend of realism and iconic design. Their contemporary rivals are the Royal Lion Knights, if you prefer shining gold armors. We haven't got any major factions since them because of Novelmore.
Speaking of knight factions, I have found that different dragon-themed factions mix along very easily. Even with non-identical emblems, a dragon knight will always look good next to another, and they strike me as the kind of edgelords who would like to outpimp their peers, so it's easy to army build them from unrelated sets and they'll look cohesive and different at the same time, making any dragon knight purchase a useful purchase. They also mix well with the Burnham Raiders from Novelmore.
If you go the official webstore route, the Playmobil Plus 6464 medieval party is an interesting set featuring various medieval guys and furniture. I think it's a rehashed set with simple character designs; the guard looks a bit kit-bashy and the old-type horse mold may clash with newer ones, but other than that it's very fine.
The webstore also has some very interesting Greek History sets, though I feel some of them may be a bit overpriced and/or kitbashy (the cyclops Polyphemus has an ogre head with a painted eye for crying out loud).