I've only read the first and second one so far but they are only slightly connected!
I'd recommend reading them in order if you want to get the references but you won't miss that many plot devices if you read them out of order.
(doulou dalu --> doulou dalu 2 --> doulou dalu 3)
neither the first nor second one are complete on mangago yet but I still think it's worth reading in order
What ordered
search either Doulou Dalu or Combat continent on here and that would be the first one in the series, after that you should read doulou dalu 2 then doulou dalu 3.
first one in the series: http://www.mangago.zone/read-manga/doulou_dalu/
second one: http://www.mangago.zone/read-manga/combat_continent_ii/
third one: http://www.mangago.zone/read-manga/douluo_dalu_3_the_legend_of_the_dragon_king/
Fourth: http://www.mangago.zone/read-manga/soul_land_iv_the_ultimate_combat/
What I said is sad of this is, none of them finished yet (༎ ෴ ༎)
gosh I didn't even realize there was a fourth one
Thanks
What order should I read all these comics in they feel like all Connected and I'm confused(￣∇￣")
┗( T﹏T )┛