Bad Machinery is great. The series before it, Scary Go Round, starts off kinda weak but ends pretty strong. The series before that, Bobbins, sucks and should be avoided. The art improves a lot towards the end of SGR and into Bad Machinery. You can read Bad Machinery without reading SGR but you'll miss some references and things will make a bit less sense so I wouldn't. Gunnerkrigg Court is godlike. The art is horrible at first but after a while it gets really really good. Dresden Codak is great story and art but fuck it will probably never finish. Read the Hob storyline and see if you want to wait around for months for updates on the current arc. There are more but it's 1:30 am so ehhhh