Gravis themed list?

Hello, I'm new to space marine (but notk and warhammer in general) and i wanted to start a gravis army since the look just feels right to me however the lack of options especially hq wise make me think it's not possible to do a full gravis list, but i still want to do it and willing to do as much kitbash as needed

but for that i need a list but i don't really know which units/detachments/chapter to chose ( i will paint them as our favorite kleptomaniac) i don't really care about it being meta just a fun list to play with my friend group (if it's relevant they play SoB, Grey knights, IG & deathguard and my other/main army is T'au)

thanks in advance