I've lived in Topeka, KS my entire life and enjoy it. I did stay in a group home in Junction City(AKA Junk Shitty) when I was around 15. Junk Shitty is right next to Ft. Riley and is a real shit hole. The whole city is pretty much made up of hood folk(other than our fine service people). Manhattan is a fun college town though and is near by. When you compare Manhattan to Lawrence Manhattan is more conservative and gun friendly. It isn't as big and there isn't as much shit to do.
Capitol City Gun Club is right down the road(about 15mins west of Topeka) on 70 if you need a place to shoot. I've been a member there for 9yrs and am very happy with the range. 300yd rifle range, 3 pistol ranges, shotgun ranges, rimfire range, and even a primitive range for knife/axe throwing. If you like to hunt there's a lot of great stuff to hunt here in KS. Some of the best bird hunting in the world, big white tale, mule dear, prong horn, coyotes galore, p-dogs out west, and bobcats.
If you're real into big city stuff you can head to KC about 2-3hrs away. There is tons of stuff to do there: museums, art galleries, music, BBQ galore, clubs, bars, etc.. If you're just trying to party at bars and pick up girls Lawrence and Manhattan are hard to beat. Manhattan will probably be your best bet as it is closer.
Quantico Arms is a gun store in Junction City and has a ton of top quality gear and weapons. They offer Mil/LEO discounts and I think a lot of soldiers buy extra shit there. In fact I think they just opened up a new store.