Kekkai Sensen is like "wow dammit NIGHTOW YOU"RE BACK". I literally started watching it, then I found out that Kekkai Sensen was written and drawn by Nightow, who did the Trigun series and NOW I'M JUST WHAT THIS IS GREAT. Because I'm a huge Trigun nerd. That's fun stuff.

In either case, yeah I really like the nonlinear plot of KS, it's tied together by some really good worldbuilding in that weird New York there (have you seen the food episode yet IT'S GREAT). I heard that a lot of the cast are VAs from Gintama so some people can't unhear those interactions heheh. Never got around to Gintama myself so I can't attest to that claim.

Lancer is awesome. If you want to hear more sass, after you finish FSN, you should watch some of Carnival Phantasm. Lancer is practically a meme there :P

For Stardust Crusaders, it's the third arc in the Jojo series, so if you haven't watched Phantom Blood and Battle Tendency (the previous seasons) you should get on that before you start Stardust Crusaders because those two seasons have the context for what happens in SC.